U.S. patent number 6,599,370 [Application Number 09/859,142] was granted by the patent office on 2003-07-29 for stabilized alkaline compositions for cleaning microelectronic substrates.
This patent grant is currently assigned to Mallinckrodt Inc.. Invention is credited to David C. Skee.
United States Patent |
6,599,370 |
Skee |
July 29, 2003 |
Stabilized alkaline compositions for cleaning microelectronic
substrates
Abstract
The invention provides aqueous alkaline compositions useful in
the microelectronics industry for stripping or cleaning
semiconductor wafer substrates by removing photoresist residues and
other unwanted contaminants. The compositions typically contain (a)
one or more metal ion-free bases at sufficient amounts to produce a
pH of about 10-13 and one or more bath stabilizing agents having at
least one pKa in the range of 10-13 to maintain this pH during use;
(b) optionally, about 0.01% to about 5% by weight (expressed as %
SiO.sub.2) of a water-soluble metal ion-free silicate; (c)
optionally, about 0.01% to about 10% by weight of one or more
chelating agents; (d) optionally, about 0.01% to about 80% by
weight of one or more water-soluble organic co-solvents; and (e)
optionally, about 0.01% to about 1% by weight of a water-soluble
surfactant.
Inventors: |
Skee; David C. (Bethlehem,
PA) |
Assignee: |
Mallinckrodt Inc. (St. Louis,
MO)
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Family
ID: |
27104249 |
Appl.
No.: |
09/859,142 |
Filed: |
May 16, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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688559 |
Oct 16, 2000 |
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Current U.S.
Class: |
134/3; 134/10;
134/2; 134/34; 134/902; 252/79.5; 438/906; 510/176; 510/401;
257/E21.228; 257/E21.255 |
Current CPC
Class: |
H01L
21/02063 (20130101); C23G 1/22 (20130101); G03F
7/425 (20130101); C23F 1/32 (20130101); C11D
7/3245 (20130101); C11D 7/261 (20130101); C23G
1/20 (20130101); C11D 11/0047 (20130101); H01L
21/02071 (20130101); C11D 3/0073 (20130101); C11D
7/3209 (20130101); C11D 7/265 (20130101); H01L
21/31133 (20130101); Y10S 134/902 (20130101); Y10S
438/906 (20130101); H01L 21/02052 (20130101) |
Current International
Class: |
C11D
3/00 (20060101); C11D 7/22 (20060101); C23G
1/22 (20060101); C11D 7/26 (20060101); C11D
7/32 (20060101); G03F 7/42 (20060101); C11D
11/00 (20060101); C23G 1/14 (20060101); C23G
001/02 () |
Field of
Search: |
;510/176,401
;134/2,3,10,34,902 ;252/79.5 ;438/906 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Abstract of JP 11-311867 Nov. 9, 1999. .
Microlectronic Engineering, 45, 197-208 (1999). .
Abstract of JP 03-93229 Apr. 18, 1991. .
Abstract of SU 791976 Sep. 7, 1980. .
Abstract of GB 1573206 Aug. 20, 1980. .
Abstract of WO 94/08276 Apr. 14, 1994. .
Abstract of JP 06-73562 Mar. 15, 1991. .
Abstract of JP 10-20511 Jan. 23, 1998. .
Abstract of JP 11-125917 May 11, 1999. .
Abstract of JP 11-133628 May 21, 1999. .
Abstract of WO 00/22662 Apr. 20, 2000. .
Abstract of EP 1031884 Aug. 31, 2000. .
Abstract of DE 2618937 Feb. 17, 1977..
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Primary Examiner: Gulakowski; Randy
Assistant Examiner: Kornakov; M.
Parent Case Text
RELATED APPLICATION
This application is a continuation-in-part of copending application
Ser. No. 09/688,559, filed Oct. 16, 2000 now allowed.
Claims
I claim:
1. A composition for stripping or cleaning integrated circuit
substrates, comprising: (a) one or more metal ion-free bases in an
amount sufficient to produce a pH of the composition of about 11 or
greater; (b) a bath stabilizing effective amount of at least one
bath stabilizing agent comprising at least one compound with at
least one pKa in the range of 10 to 13; (c) water; and (d) from
about 0.01% to about 5% by weight of the composition of a
water-soluble metal ion-free silicate.
2. The composition of claim 1 wherein the metal ion-free bases are
present in sufficient amounts to produce a pH of from about 11 to
about 13.
3. The composition of claim 1 wherein the at least one bath
stabilizing agent comprises at least one compound with at least one
pKa in the range of 11 to 12.5.
4. The composition of claim 1 wherein the at least one bath
stabilizing agent is selected from the group consisting of acetone
oxime, hydrogen peroxide, salicylic acid, 5-sulfosalicylic acid,
phosphoric acid, 2-hydroxypyridine, 4-hydroxypyridine, resorcinol,
2-methylresorcinol, salicylaldoxime, 2-methyl-1,5-pentanediamine,
1,2-ethanediamine, 1,3-propanediamine, 1,4-butanediamine,
1,6-hexanediamine, 1,8-octanediamine, 1,12-dodecanediamine,
1,3-diaminopentane and orcinol.
5. The composition of claim 1 wherein the at least one bath
stabilizing agent is added to a concentration of from 0.1 to 50% by
weight.
6. The composition of claim 1 wherein the at least one bath
stabilizing agent comprises at least one compound selected from the
group consisting of 2-hydroxypyridine, 4-hydroxypyridine,
resorcinol and 2-methylresorcinol.
7. The composition of claim 1 wherein the composition further
contains one or more chelating or complexing agents and the
concentration of chelating or complexing agents is from about 0.01%
to about 10% by weight.
8. The composition according to claim 7 wherein the bath
stabilizing agent is hydrogen peroxide and the chelating or
complexing agent is selected from the group consisting of
(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA) and phosphonic
acids.
9. The composition of claim 7 wherein the chelating or complexing
agent is selected from the group consisting of aminocarboxylic
acids and phosphonic acids.
10. The composition of claim 7 wherein the chelating or complexing
agent is selected from the group consisting of
(ethylenedinitrilo)tetraacetic acid, diethylenetriaminepentaacetic
acid, triethylenetetraminehexaacetic acid,
1,3-diamino-2-hydroxypropane-N,N,N',N'-tetraacetic acid,
N,N,N',N'-ethylenediaminetetra(methylenephosphonic acid),
cis-1,2-cyclohexylenedinitrilo)tetraacetic acid,
1,5,9-triazacyclododecane-N,N',N"-tris(methylenephosphonic acid)
(DOTRP),
1,4,7,10-tetraazacyclododecane-N,N',N",N'"-tetrakis(methylenephosphonic
acid) (DOTP), nitrilotris(methylene) triphosphonic acid,
diethylenetriaminepenta(methylenephosphonic acid),
aminotri(methylenephosphonic acid),
1-hydroxyethylene-1,1-diphosphonic acid, bis(hexamethylene)triamine
phosphonic acid,
1,4,7-triazacyclononane-N,N',N"-tris(methylenephosphonic acid
(NOTP), ethylenediaminetetra(methylenephosphonic acid),
2-phosphonobutane-1,2,4-tricarboxylic acid and
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid.
11. The composition of claim 1 further comprising one or more
water-soluble organic co-solvents.
12. The composition of claim 11 wherein the concentration of
water-soluble organic co-solvents is from about 0.1% to about 30%
by weight.
13. The composition of claim 11 wherein said water-soluble organic
co-solvent is selected from the group consisting of
1-hydroxyalkyl-2-pyrrolidinones alcohols and polyhydroxy
compounds.
14. The composition of claim 11 wherein said water-soluble organic
co-solvent is glycerol.
15. The composition of claim 1 further containing one or more
water-soluble surfactants.
16. The compositions of claim 15 wherein the concentration of
water-soluble surfactants is from about 0.01% to about 1% by
weight.
17. The composition of claim 1 wherein the base is selected from
the group consisting of hydroxides and organic amines.
18. The composition of claim 17 wherein the base is selected from
the group consisting of quaternary ammonium hydroxides, ammonium
hydroxides, and organic amines.
19. The composition of claim 1 wherein the base is selected from
the group consisting of choline, tetrabutylammonium hydroxide,
tetramethylammonium hydroxide, monomethyltriethanolammonium
hydroxide, monomethyltriethylammonium hydroxide, tetraethylammonium
hydroxide, tetrapropylammonium hydroxide, tetraethanolammonium
hydroxide, 2-methyl-1,5-pentanediamine, 1,2-ethanediamine,
1,3-propanediamine, 1,4-butanediamine, 1,5-pentanediamine,
1,6-hexanadiamine, 1,7-heptanediamine, 1,8-octanediamine,
1,9-nonanediamine, 1,10-decanediamine, 1,11-undecanediamine,
1,12-dodecanediamine and 1,3-diaminopentane.
20. The composition of claim 1 wherein the water-soluble metal
ion-free silicate is selected from the group consisting of ammonium
silicates and quaternary ammonium silicates.
21. The composition of claim 1 wherein the water-soluble metal
ion-free silicate is tetramethylammonium silicate.
22. The composition of claim 1 containing from about 0.1-25% by
weight tetramethylammonium hydroxide and about 0.01-1% by weight of
tetramethylammonium silicate.
23. The composition of claim 22 further containing from about
0.01-1% by weight trans-(1,2-cyolohexylenedinitrilo)tetraacetic
acid.
24. The composition of claim 1 wherein the bath stabilizing agent
is selected from the group consisting of acetone oxime, hydrogen
peroxide, salicylic acid, 5-sulfosalicylic acid, phosphoric acid,
2-hydroxypyridine, 4-hydroxypyridine, resorcinol,
2-methylresorcinol, salicylaldoxime, 2-methyl-1,5-pentanediamine,
1,2-ethanediamine, 1,3-propanediamine, 1,4-butanediamine,
1,5-pentanediamine, 1,6-hexanediamine, 1,7-heptanediamine,
1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine,
1,11-undecanediamine, 1,12-dodecanediamine, 1,3-diaminopentane,
orcinol, hydrogen germanate, adenosine, cytosine, arginine,
benzil-.alpha.-dioxime, benzimidazole, benzoylhydrazine,
benzoylpyruvic acid, berberine, biguanide,
2-butyl-1-methyl-2-pyrroline, calmagite, chrome azurol S, chrome
dark blue, cumene hydroperoxide, 1,2-cyclohexylenedinitriloacetic
acid, cytidine, diethylbiguanide, diguanide,
2,4-dihydroxy-1-phenylazobenzene, 2,6-dihydroxypurine,
dimethylbiguanide, ethylbiguanide, ethylenebiguanide, ethyl methyl
ketoxime, 1-ethyl-2-methyl-2-pyrroline, 4-formyl-3-methoxypyridine,
guanine, guanosine, 2-hydroxybenzaldehyde oxime,
N-(hydroxyethyl)biguanide, 2-hydroxyquinoline, hypoxanthene,
inosine, 5-iodohistamine, 2,2'-methylenebis(4-chlorophenol),
2-methyl-8-hydroxyquinoline, 4-methyl-8-hydroxyquinoline,
1-methylxanthine, phenylalanylarginine, silicic acid, sparteine,
thorin, toluhydroquinone, tyrosylarginine, xanthosine, acetamidine,
trifluoroethanol, trichloroethanol, pyridine-4-aldehyde,
hypoxanthine, uric acid, pyrrolidine, diethylamine, piperidine,
3-amino-3-methylpentane, diisopropylamine, saccharin,
2,2,4-trimethylpiperidine, dibutylamine,
L-3,4-dihydroxyphenylalanine, 2,2,6,6-tetramethylpiperidine,
5-hydroxytryptamine, butylcyclohexylamine, 2-phenylbenzimidazole,
2-methyl-2-butanethiol, 2-methyl-2-propanethiol, dihexylamine,
methoxypyridine, 1,4-dihydroxy-2,3,5,6-tetramethylbenzene,
glutarimide, malanonitrile, benzamidine, 4-hydroxyquinoline,
4,4,9,9-tetramethyl-5,8-diazodcdecane-2,11-diamine,
1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine,
1,9-nonanediamine 1,10-decanediamine, 1,12-dodecanediamine,
hydrogen hyponitrite, hydroxylamine-N,N-disulfonic acid,
(1,2-cyclohexylenedinitrilo)tetraacetic aoid (CyDTA),
diethylenetriaminepenta(methylenephosphonic acid) (DETPA), lysine,
tyrosine, 3-amino-N,N-bis(2-aminoethyl)propylamine,
tris(2-aminoethyl)amine, 3-(cyclohexylamino)-1-propanesulfonic
acid, methylamine, dimethylamine, ethylamine, cysteamine,
1,2-ethanediamine, .alpha.-alanine, .beta.-alanine, azetidine,
methylglycine, cysteine, propylamine, 1,3-propanediamine,
4-aminobutanoic acid, 2-methylalanine, homocysteine,
2,4-diaminobutanoic acid, butylamine, 1,4-butanediamine,
2,3-butanediamine, 1,2-dimethylaminoethane, proline,
N-methylpyrrolidine, 5-aminopentanoic acid, N-propylglycine,
ornithine, 1-amino-2,2-dimethylpropane, diethylmethylamine,
3-methyl-1-butanamine, 2-methyl-2-butanamine, 3-pentanamine,
pentylamine, 1,5-pentanediamine, 2-pyridinecarboxaldehyde oxime,
hydroquinone, pipecolic acid, cyclohexylamine,
1,2-dimethylpyrrolidine, 1-methylpiperidine, 6-aminohexanoic acid,
hexylamine, triethylamine, cresol, 2-dimethylaminopurine,
1,2-dimethylpiperidine, 1-ethylpiperidine, 2-heptanamine,
heptylamine, tyramine, dopamine, N-methyl-2-heptanamine,
octylamine, 1-butylpiperidine, nonylamine, tryptamine, d-ephedrine,
bornylamine, neobomylamine, decylamine, undecylamine, dodecylamine,
tridecylamine, tetradecylamine, L-thyroxine, pentadecylamine,
hexadecylamine, octadecylamine, 4-aminobutyric acid,
2-amino-2-methylpropionic acid, 3-aminopropionic acid,
ethylenediaminetetraacetic acid (EDTA),
N,N'-dimethylethyleneamine-N,N'-diacetic acid, methylaminodiacetic
acid, 2-methyl-2-propylamine, nitrilotriacetic acid,
1,2,4-triazole, chloral, ethtyl acetoacetate, phenol,
.beta.-phenylethylboric acid, nitromethane, thioglycollic acid,
ethyl mercaptan, cyanamide, docosylamine, tert-butylamine,
trimethylamine, 2-mercaptoethylamine, 5-aminovaleric acid,
4-aminophenol, hydrogen hypoiodite, aminopropylmorpholine,
ethanethiol, carbonic acid, tetramethylammonium carbonate, ammonium
bicarbonate, ammonium carbonate, choline bicarbonate, carbon
dioxide+water, threonine, hydrogen thiophosphate, sarcosine,
4-methoxyphenol, 4-ethoxyphenol, 4-propoxyphenol, 4-butoxyphenol,
4-pentoxyphenol, 5-hydroxymethylcytosine, oxaloacetic acid, cumene
hydroperoxide, diguanidine, hydrogen sulfide and hydrogen
peroxophosphate.
25. A composition for stripping or cleaning integrated circuit
substrates, comprising: (a) one or more metal ion-free bases
present in the composition in an amount sufficient to produce a pH
of the composition of from about 11 to 13; (b) from about 0.1 to
about 50% by weight of the composition of at least one bath
stabilizing agent comprising at least one compound with at least
one pKa in the range of 10 to 13; and (c) water; (d) with the
proviso that when the semiconductor wafer substrate has aluminum or
aluminum alloy present the composition also contains from about
0.01% to about 5% by weight of the composition of a water-soluble
metal ion-free silicate.
26. A method for cleaning semiconductor wafer substrates having
copper, aluminum or alloys thereof, comprising: contacting a
semiconductor wafer substrate having a substrate surface for a time
and at a temperature sufficient to clean unwanted contaminants and
residues from said substrate surface with a composition comprising:
(a) one or more metal ion-free bases in an amount sufficient to
produce a pH of the composition of about 11 or greater; (b) a bath
stabilizing effective amount of at least one bath stabilizing agent
comprising at least one compound with at least one pKa in the range
of 10 to 13; (c) water; and (d) from about 0.01% to about 5% by
weight of the composition of a water-soluble metal ion-free
silicate.
27. The method of claim 26 wherein the semiconductor wafer
substrate is in contact with the composition for from about 1 to
about 30 minutes.
28. The method of claim 26 wherein the semiconductor wafer
substrate is in contact with the composition at a temperature of
from about 10.degree. C. to about 85.degree. C.
29. The method of claim 26 further comprising a rinsing and a
drying step.
30. The method of claim 26 wherein the composition contains metal
ion-free bases in sufficient amounts to produce a pH of from about
10 to about 13.
31. The method of claim 26 wherein the at least one bath
stabilizing agent comprises at least one compound with at least one
pKa in the range of 11 to 12.5.
32. The method of claim 26 wherein the at least one bath
stabilizing agent is selected from the group consisting of acetone
oxime, hydrogen peroxide, salicylic acid, 5-sulfosalicylic acid,
phosphoric acid, 2-hydroxypyridine, 4-hydroxypyridine, resorcinol,
2-methylresorcinol, salicylaldoxime, 2-methyl-1,5-pentanediamine,
1,2-ethanediamine, 1,3-propanediamine, 1,4-butanediamine,
1,6-hexanediamine, 1,8-octanediamine, 1,12-dodecanediamine,
1,3-diaminopentane and orcinol.
33. The method of claim 26 wherein the at least one bath
stabilizing agent is added to a concentration of from 0.1 to 50% by
weight.
34. The method of claim 26 wherein the at least one bath
stabilizing agent is selected from the group consisting of
2-hydroxypyridine, 4-hydroxypyridine, resorcinol and
2-methylresorcinol.
35. The method of claim 26 wherein the composition further contains
one or more chelating or complexing agents in the composition and
wherein the concentration of chelating or complexing agents is from
about 0.01% to about 10% by weight.
36. The method according to claim 35 wherein the bath stabilizing
agent is hydrogen peroxide and the chelating or complexing agent is
selected from the group consisting of
(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA) and phosphonic
acids.
37. The method of the claim 35 wherein the chelating or complexing
agent is selected from the group consisting of aminocarboxylic
acids and phosphonic acids.
38. The method of claim 35 wherein the chelating agent is selected
from the group consisting of (ethylenedinitrilo)tetraacetic acid,
diethylenetriaminepentaacetic acid, triethylenetetraminehexaacetic
acid, 1,3-diamino-2-hydroxypropane-N,N,N',N'-tetraacetic acid,
N,N',N'-ethylenediaminetetra(methylenephosphonic acid),
cis-(1,2-cyclohexylenedinitrilo)tetraacetic acid,
1,5,9-triazacyolododecane-N,N',N"-tris(methylenephosphonic acid)
(DOTRP), 1,4,7,10-tetraazacyclododecane-N,N',N",N'"-tetrakis
(methylenephosphonic acid) (DOTP),
nitrilotris(methylene)triphosphonic acid,
diethylenetriaminepenta(methylenephosphonic acid),
aminotri(methylenephosphonic acid),
1-hydroxyethylene-1,1-diphosphonic acid, bis(hexamethylene)triamine
phosphonic acid,
1,4,7-triazacyclononane-N,N',N"-tris(methylenephosphonic acid)
(NOTP), ethylenediaminetetraa(methylenephosphonic acid),
2-phosphonobutane-1,2,4-tricarboxylic acid, and
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid.
39. The method of claim 26 wherein the composition further contains
one or more water-soluble organic co-solvents in the
composition.
40. The method of claim 39 wherein the concentration of
water-soluble organic co-solvents is from about 0.1% to about 30%
by weight.
41. The method of claim 39 wherein said water-soluble organic
co-solvent is selected from the group consisting of
1-hydroxyalkyl-2-pyrrolidinones, alcohols and polyhydroxy
compounds.
42. The method of claim 39 wherein said water-soluble organic
co-solvent is glycerol.
43. The method of claim 26 wherein the composition further contains
one or more water-soluble surfactants in the composition.
44. The method of claim 43 further wherein the concentration of
water-soluble surfactants is from about 0.01% to about 1% by
weight.
45. The method of claim 26 wherein the base in the composition is
selected from the group consisting of hydroxides and organic
amines.
46. The method of claim 45 wherein the base in the composition is
selected from the group consisting of quaternary ammonium
hydroxides, ammonium hydroxides, and organic amines.
47. The method of claim 26 wherein the base in the composition is
selected from the group consisting of choline, tetrabutylammonium
hydroxide, tetramethylammonium hydroxide,
monomethyltriethanolammonium hydroxide, monomethyltriethylammonium
hydroxide, tetraethylammonium hydroxide, tetrapropylammonium
hydroxide, tetraethanolammonium hydroxide,
2-methyl-1,5-pentanediamine, 1,2-ethanediamine, 1,3-propanediamine,
1,4-butanediamine, 1,5-pentanediamine, 1,6-hexanediamine,
1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine,
1,10-decanediamine, 1,11-undecanediamine, 1,12-dodecanediamine and
1,3-diaminopentane.
48. The method of claim 26 wherein the water-soluble metal ion-free
silicate in the composition is selected from the group consisting
of ammonium silicates and quaternary ammonium silicates.
49. The method of claim 26 wherein the water-soluble metal ion-free
silicate in the composition is tetramethylammonium silicate.
50. The method of claim 26 wherein the composition contains from
about 0.1-25% by weight tetramethylammonium hydroxide and about
0.01-1% by weight of tetramethylammonium silicate.
51. The method of claim 50 wherein the composition further contains
0.01-1% by weight of a chelating or complexing agent selected from
the group consisting of (1,2-cyclohexylenedinitrilo)tetraacetic
acid or a phosphonic acid.
52. The method of claim 26 wherein the bath stabilizing agent is
selected from the group consisting of acetone oxime, hydrogen
peroxide, salicylic acid, 5-acid, 5-sulfosalicylic acid, phosphoric
acid, 2-hydroxypyridine, 4-hydroxypyridine, resorcinol,
2-methylresorcinol, salicylaldoxime, 2-methyl-1,5-pentanediamine,
1,2-ethanediamine, 1,3-propanediamine, 1,4-butanediamine,
1,5-pentanediamine, 1,6-hexanediamine, 1,7-heptanediamine,
1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine,
1,11-undecanediamine, 1,12-dodecanediamine, 1,3-diaminopentane,
orcinol, hydrogen germanate, adenosine, cytosine, arginine,
benzil-.alpha.-dioxime, benzimidazole, banzoylhydrazine,
benzoylpyruvic acid, berberine, biguanide,
2-butyl-1-methyl-2-pyrroline, calmagite, chrome azurol S, chrome
dark blue, cumene hydroperoxide, 1,2-cyclohexylenedinitriloacetic
acid, cytidine, dimethylbiguanide, diguanide,
2,4-dihydroxy-1-phenylazobenzene, 2,6-dihydroxypurine,
dimethylbiguanide, ethylbiguanide, ethylenebiguanide, ethyl methyl
ketoxime, 1-ethyl-2-methyl-2-pyrroline, 4-formyl-3-methoxypyridine,
guanine, guanosine, 2-hydroxybenzaldehyde oxime,
N-(hydroxyethyl)biguanide, 2-hydroxyquinoline, hypoxanthene,
inosine, 5-iodohistamine, 2,2'-methylenebis(4-chlorophenol),
2-methyl-8-hydroxyquinoline, 4-methyl-8-hydroxyquinoline,
1-methylxanthine, phenylalanylarginine, silicic acid, sparteine,
thorin, toluhydroquinone, tyrosylarginine, xanthosine, acetamidine,
trifluoroethanol, trichloroethanol, pyridine-4-aldehyde,
hypoxanthine, uric acid, pyrrolidine, diethylamine, piperidine,
3-amino-3-methylpentane, diisopropylamine, saccharin,
2,2,4-trimethylpiperidine, dibutylamine,
L-3,4-dihydroxyphenylalanine, 2,2,6,6-tetramethylpiperidine,
5-hydroxytryptamine, butylcyclohexylamine, 2-phenylbenzimidazole,
2-methyl-2-butanethiol, 2-methyl-2-propanethiol, dihexylamine,
methoxypyridine, 1,4-dihydroxy-2,3,5,6-tetramethylbenzene,
glutarimide, malanonitrile, benzamidine, 4-hydroxyquinoline,
4,4,9,9-tetramethyl-5,8-diazododecane-2,11-dismine,
1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine,
1,9-nonanediamine 1,10-decanediamine, 1,12-dodecanediamine,
hydrogen hyponitrite, hydroxylamine-N,N-disulfonic acid,
(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA),
diethylenetriaminepenta(methylenephosphonic acid) (DETPA), lysine,
tyrosine,
3-amino-N,N-bis(2-aminoethyl)propylamine)tris(2-aminoethyl)amine,
3-(cyclohexylamino)-1-propanesulfonic acid, methylamine,
dimethylamine, ethylamine, cysteamine, 1,2-ethanediamine,
.alpha.-alanine, .beta.-alanine, azetidine, methylglycine,
cysteine, propylamine, 1,3-propanediamine, 4-aminobutanoic acid,
2-methylalanine, homocysteine, 2,4-diaminobutanoic acid,
butylamine, 1,4-butanediamine, 2,3-butanediamine,
1,2-dimethylaminoethane, proline, N-methylpyrrolidine,
5-aminopentanoic acid, N-propylglycine, ornithine,
1-amino-2,2-dimethylpropane, diethylmethylamine,
3-methyl-1-butanamine, 2-methyl-2-butanamine, 3-pentanamine,
pentylamine, 1,5-pentanediamine, 2-pyridinecarboxaldehyde oxime,
hydroquinone, pipecolic acid, cyclohexylamine,
1,2-dimethylpyrrolidine, 1-methylpiperidine, 6-aminohexanoic acid,
hexylamine, triethylamine, cresol, 2-dimethylaminopurine,
1,2-dimethylpiperidine, 1-ethylpiperidine, 2-heptanamine,
heptylamine, tyramine, dopamine, N-methyl-2-heptanamine,
octylamine, 1-butylpiperidine, nonylamine, tryptamine, d-ephedrine,
bornylamine, neobomylamine, decylamine, undecylamine, dodecylamine,
tridecylamine, tetradecylamine, L-thyroxine, pentadecylamine,
hexadecylamine, octadecylamine, 4-aminobutyric acid,
2-amino-2-methylpropionic acid, 3-aminopropionic acid,
ethylenediaminetetreacetic acid (EDTA),
N,N'-dimethylethyleneamine-N,N'-diacetic acid, methylaminodiacetic
acid, 2-methyl-2-propylamine, nitrilotriacetic acid,
1,2,4-triazole, chloral, ethtyl acetoacetate, phenol,
.beta.-phenylethyboric acid, nitromethane, thioglycollic acid,
ethyl mercaptan, cyanamide, docosylamine, tert-butylamine,
trimethylamine, 2-mercaptoethylamine, 5-aminovaleric acid,
4-aminophenol, hydrogen hypoiodite, aminopropylmorpholine,
ethanethiol, carbonic acid, tetramethylammonium carbonate, ammonium
bicarbonate, ammonium carbonate, choline bicarbonate, carbon
dioxide+water, threonine, hydrogen thiophosphate, sarcosine,
4-methoxyphenol, 4-ethoxyphenol, 4-propoxyphenol, 4-butoxyphenol,
4-pentoxyphenol, 5-hydroxymethylcytosine, oxaloacetic acid, cumene
hydroperoxide, diguanidine, hydrogen sulfide and hydrogen
peroxophosphate.
53. A method for cleaning semiconductor wafer substrates,
comprising: contacting a semiconductor wafer substrate having a
substrate surface for a time and at a temperature sufficient to
clean unwanted contaminants and residues from said substrate
surface with a composition comprising: (a) one or more metal
ion-free bases present in the composition in an amount to provide a
pH of the composition of from about 11 to 13; (b) at least one bath
stabilizing agent comprising at least one compound with at least
one pKa in the range of 10 to 13, with the one or more bath
stabilizing agent present in the composition in an amount of from
about 0.1 to about 50% by weight of the composition; and (c)
water.
54. The method of claim 52 wherein said at least one bath
stabilizing agent is added to a concentration of from 0.1 to 50% by
weight of the composition.
55. The method of claim 52 wherein said at least one bath
stabilizing agent is selected from the group consisting of
2-hydroxypyridine, 4-hydroxypyridine, resorcinol and 2-methyl
resorcinol.
56. The method of claim 54 wherein said at least one bath
stabilizing agent is added to a concentration of from 0.1 to 35% by
weight of the composition.
57. A method of extending bath-life of an aqueous alkaline
composition for stripping or cleaning integrated circuit substrates
wherein said composition comprises: (a) one or more metal ion-free
bases in an amount sufficient to produce a pH of the composition of
about 11 or greater; (b) water; and (c) from about 0.01% to about
5% by weight of the composition of a water-soluble metal ion-free
silicate; said method comprising adding to said composition a bath
stabilizing effective amount of at least one bath stabilizing agent
comprising at least one compound having at least one pKa in the
range of 10 to 13.
58. The method of claim 57 wherein said at least one bath
stabilizing agent comprises a compound with at least one pKa in the
range of 11 to 12.5.
59. The method of claim 57 wherein said at least one bath
stabilizing agent is selected from the group consisting of acetone
oxime, hydrogen peroxide, salicylic acid, 5-sulfosalicylic acid,
phosphoric acid, 2-hydroxypyridine, 4-hydroxypyridine, resorcinol,
2-methylresorcinol, salicylaldoxime, 2-methyl-1,5-pentanediamine,
1,2-ethanediamine, 1,3-propanediamine, 1,4-butanediamine,
1,6-hexanediamine, 1,8-octanediamine, 1,12-dodecanediamine,
1,3-diaminopentane and orcinol.
60. The method according to claim 57 wherein the bath stabilizing
agent is selected from the group consisting of acetone oxime,
hydrogen peroxide, salicylic acid, 5-sulfosalicylic acid,
phosphoric acid, 2-hydroxypyridine, 4-hydroxypyridine, resorcinol,
2-methylresorcinol, salicylaldoxime, 2-methyl-1,5-pentanediamine,
1,2-ethanediamine, 1,3-propanediamine, 1,4-butanediamine,
1,5-pentanediamine, 1,6-hexanediamine, 1,7-heptanediamine,
1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine,
1,11-undecanediamine, 1,12-dodecanediamine, 1,3-diaminopentane,
orcinol, hydrogen germanate, adenosine, cytosine, arginine,
benzil-.alpha.-dioxime, benzimidazole, benzimidazole,
benzoylhydrazine, benzoylpyruvic acid, berberine, biguanide,
2-butyl-1-methyl-2-pyrroline, calmagite, chrome azurol S, chrome
dark blue, cumene hydroperoxide, 1,2-cyolohexylenedinitriloacetic,
cytidine, diethylbiguanide, diguanide,
2,4-dihydroxy-1-phenylazobenzene, 2,6-dihydroxypurine,
dimethylbiguanide, ethylbiguanide, ethylenebiguanide, ethyl methyl
ketoxime, 1-ethyl-2-methyl-2-pyrroline, 4-formyl-3-methoxypyridine,
guanine, guanosine, 2-hydroxybenzaldehyde oxime,
N-(hydroxyethyl)biguanide, 2-hydroxyquinoline, hypoxanthene,
inosine, 5-iodohistamine, 2,2'-methylenebis(4-chrorophenol),
2-methyl-8-hydroxyquinoline, 4-methyl-8-hydroxyquinoline,
1-methylxanthine, phenylalanylarginine, silicic acid, sparteine,
thorin, toluhydroquinone, tyrosylarginine, xanthosine, acetamidine,
trifluoroethanol, trichloroethanol, pyridine-4-aldehyde,
hypoxanthine, uric acid, pyrrolidine, diethylamine, piperidine,
3-amino-3-methylpentane, diisopropylamine, saccharin,
2,2,4-trimethylpiperidine, dibutylamine,
L-3,4-dihydroxyphenylalanine, 2,2,6,6-tetramethylpiperidine,
5-hydroxytryptamine, butylcyclohexylamine, 2-phenylbenzimidazole,
2-methyl-2-butanethiol, 2-methyl-2-propanethiol, dihexylamine,
methoxypyridine, 1,4-dihydroxy-2,3,5,6-tetramethylbenzene,
glutarimide, malanonitrile, benzamidine, 4-hydroxyquinoline,
4,4,9,9-tetramethyl-5,8-diazododecane-2,11-diamine,
1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine,
1,9-nonanediamine, 1,10-decanediamine, 1,12-dodecanediamine,
hydrogen hyponitrite, hydroxylamine-N,N-disulfonic acid,
(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA),
diethylenetriaminepenta(methylenephosphonic acid) (DETPA), lysine,
tyrosine, 3-amino-N,N-bis(2-aminoethyl)propylamine,
tris(2-aminoethyl)amine, 3-(cyclohexylamino)-1-propanesulfonic
acid, methylamine, dimethylamine, ethylamine, cysteamine,
1,2-ethanediamine, .alpha.-alanine, .beta.-alanine, azetidine,
methylglycine, cysteine, propylamine, 1,3-propanediamine,
4-aminobutanoic acid, 2-methylalanine, homocysteine,
2,4-diaminobutanoic , butylamine, 1,4-butanediamine,
2,3-butanediamine, 1,2-dimethylaminoethane, proline,
N-methylpyrrolidine, 5-aminopentanoic acid, N-propylglycine,
ornithine, 1-amino-2,2-dimethylpropane, diethylmethylamine,
3-methyl-1-butanamine, 2-methyl-2-butanamine, 3-pentanamine,
pentylamine, 1,5-pentanediamine, 2-pyridinecarboxaldehyde oxime,
hydroquinone, pipecolic acid, cyclohexylamine,
1,2-dimethylpyrrolidine, 1-methylpiperidine, 6-aminohexanoic acid,
hexylamine, triethylamine, cresol, 2-dimethylaminopurine,
1,2-dimethylpiperidine, 1-ethylpiperidine, 2-heptanamine,
heptylamine, tyramine, dopamine, N-methyl-2-heptanamine,
octylamine, 1-butylpiperidine, nonylamine, tryptamine, d-ephedrine,
bornylamine, neobornylamine, decylamine, undecylamine,
dodecylamine, tridecylamine, tetradecylamine, L-thyroxine,
pentadecylamine, hexadecylamine, octadecylamine, 4-aminobutyric
acid, 2-amino-2-methylpropionic acid, 3-aminopropionic acid,
ethylenediaminetetraacetic acid (EDTA),
N,N'-dimethylethyleneamine-N,N'-diacetic acid, methylaminodiacetic
acid, 2-methyl-2-propylamine, nitrilotriacetic acid,
1,2,4-triazole, chloral, ethtyl acetoacetate, phenol,
.beta.-phenylethylboric acid, nitromethane, thioglycoilic acid,
ethyl mercaptan, cyanamide, docosylamine, tert-butylamine,
trimethylamine, 2-mercaptoethylamine, 5-aminovaleric acid,
4-aminophenol, hydrogen hypoiodite, aminopropylmorpholine,
ethanethiol, carbonic acid, tetramethylammonium carbonate, ammonium
bicarbonate, ammonium carbonate, choline bicarbonate, carbon
dioxide+water, threonine, hydrogen thiophosphate, sarcosine,
4-methoxyphenol, 4-ethoxyphenol, 4-propoxyphenol, 4-butoxyphenol,
4-pentoxyphenol, 5-hydroxymethylcytosine, oxaloacetic acid, cumene
hydroperoxide, diguanidine, hydrogen sulfide and hydrogen
peroxophosphate.
Description
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
This invention relates to compositions useful in the
microelectronics industry for cleaning semiconductor wafer
substrates. Particularly, this invention relates to alkaline
stripping or cleaning compositions containing bath stabilizing
agents that are used for cleaning wafers having metal lines and
vias by removing metallic and organic contamination without
damaging the integrated circuits.
DESCRIPTION OF THE PRIOR ART
An integral part of microelectronic fabrication is the use of
photoresists to transfer an image from a mask or reticle to the
desired circuit layer. After the desired image transfer has been
achieved, an etching process is used to form the desired
structures. The most common structures formed in this way are metal
lines and vias.
The metal lines are used to form electrical connections between
various parts of the integrated circuit that lie in the same
fabrication layer. The vias are holes that are etched through
dielectric layers and later filled with a conductive metal. These
are used to make electrical connections between different vertical
layers of the integrated circuit. A halogen containing gas is
generally used in the processes used for forming metal lines and
vias.
After the etching process has been completed, the bulk of the
photoresist may be removed by either a chemical stripper solution
or by an oxygen plasma ashing process. The problem is that these
etching processes produce highly insoluble metal-containing
residues that may not be removed by common chemical stripper
solutions. Also, during an ashing process the metal-containing
residues are oxidized and made even more difficult to remove,
particularly in the case of aluminum-based integrated circuits.
See, "Managing Etch and Implant Residue," Semiconductor
International, August 1997, pages 56-63.
An example of such an etching process is the patterning of metal
lines on an integrated circuit. In this process, a photoresist
coating is applied over a metal film then imaged through a mask or
reticle to selectively expose a pattern in the photoresist coating.
The coating is developed to remove either exposed or unexposed
photoresist, depending on the tone of the photoresist used, and
produce a photoresist on the metal pattern. The remaining
photoresist is usually hard-baked at high temperature to remove
solvents and optionally to cross-link the polymer matrix. The
actual metal etching step is then performed. This etching step
removes metal not covered by photoresist through the action of a
gaseous plasma. Removal of such metal transfers the pattern from
the photoresist layer to the metal layer. The remaining photoresist
is then removed ("stripped") with an organic stripper solution or
with an oxygen plasma ashing procedure. The ashing procedure is
often followed by a rinsing step that uses a liquid organic
stripper solution. However, the stripper solutions currently
available, usually alkaline stripper solutions, leave insoluble
metal oxides and other metal-containing residues on the integrated
circuit.
Another example of such an etching process is the patterning of
vias (interconnect holes) on an integrated circuit. In this
process, a photoresist coating is applied over a dielectric film
then imaged through a mask or reticle to selectively expose a
pattern in the photoresist coating. The coating is developed to
remove either exposed or unexposed photoresist, depending on the
tone of the photoresist used, and produce a photoresist on the
metal pattern. The remaining photoresist is usually hard-baked at
high temperature to remove solvents and optionally to cross-link
the polymer matrix. The actual dielectric etching step is then
performed. This etching step removes dielectric not covered by
photoresist through the action of a gaseous plasma. Removal of such
dielectric transfers the pattern from the photoresist layer to the
dielectric layer. The remaining photoresist is then removed
("stripped") with an organic stripper solution or with an oxygen
plasma ashing procedure. Typically, the dielectric is etched to a
point where the underlying metal layer is exposed. A titanium or
titanium nitride anti-reflective or diffusion barrier layer is
typically present at the metal/dielectric boundary. This boundary
layer is usually etched through to expose the underlying metal. It
has been found that the action of etching through the titanium or
titanium nitride layer causes titanium to be incorporated into the
etching residues formed inside of the via. Oxygen plasma ashing
oxidizes these via residues making them more difficult to
remove.
The use of alkaline strippers on microcircuit containing metal
films has not always produced quality circuits, particularly when
used with metal films containing aluminum or various combinations
or alloys of active metals such as aluminum or titanium with more
electropositive metals such as copper or tungsten. Various types of
metal corrosion, such as corrosion whiskers, pitting, notching of
metal lines, have been observed due, at least in part, to reaction
of the metals with alkaline strippers. Further it has been shown,
by Lee et al., Proc. Interface '89, pp. 137-149, that very little
corrosive action takes place until the water rinsing step that is
required to remove the organic stripper from the wafer. The
corrosion is evidently a result of contacting the metals with the
strongly alkaline aqueous solution that is present during rinsing.
Aluminum metal is known to corrode rapidly under such conditions,
Ambat et al., Corrosion Science, Vol. 33 (5), p. 684. 1992.
Prior methods used to avoid this corrosion problem employed
intermediate rinses with non-alkaline organic solvents such as
isopropyl alcohol. However, such methods are expensive and have
unwanted safety, chemical hygiene, and environmental
consequences.
The prior art discloses several organic strippers used to remove
bulk photoresist after the etching process. U.S. Pat. Nos.
4,765,844, 5,102,777 and 5,308,745 disclose photoresist strippers
comprising various combinations of organic solvents. These
strippers, however, are not very effective on wafers that have been
"ashed" with oxygen plasmas as described above. Some photoresist
strippers attempt to address this problem by adding additional
water and an organic corrosion inhibitor such as catechol. Such
compositions are disclosed in U.S. Pat. Nos. 5,482,566, 5,279,771,
5,381,807, 5,334,332, 5,709,756, 5,707,947, and 5,419,779 and in WO
9800244. In some cases, the hydrazine derivative, hydroxylamine, is
added as well. The use of catechol or hydroxylamine in stripping
compositions gives rise to various environmental, safety, and
health concerns.
The use of an aqueous solution containing a quaternary ammonium
hydroxide and a quaternary ammonium salt of silicic acid or alkyl
silicate has been used as photoresist developers for positive tone
photoresists in disclosures such as JP 1120552 (published May 12,
1989) and U.S. Pat. No. 4,628,023. Positive tone photoresist
developers are used to remove patterned bulk photoresist after
exposure to a solublizing radiation source. Developers are used
prior to etching for pattern transfer to the exposed metal or
dielectric substrate where metallic residues are generated. The
object of the use of a quaternary ammonium salt of silicic acid in
this disclosure is to prevent corrosion of metal substrates while
removing the soluble bulk organic photoresist and not the removal
of metal-rich post etch residues present on metal substrates
without causing corrosion.
In U.S. Pat. Nos. 6,020,292; 5,817,610 and EP 829,768 the use of a
quaternary ammonium silicate, quaternary ammonium hydroxide and
water is disclosed for use in removing plasma etch residues. In
U.S. Pat. No. 5,759,973 and EP 828,197 the use of a quaternary
ammonium silicate, an amine compound, water and optionally an
organic polar solvent is disclosed for use as a stripping and
cleaning composition. In WO 9960448, many silicate containing
compositions are described that effectively remove metal-containing
ash residues without causing corrosion.
The use of a quaternary ammonium hydroxide in photoresist strippers
is disclosed in U.S. Pat. Nos. 4,776,892, 5,563,119; JP 09319098
A2; EP 578507 A2; WO 9117484 A1 and U.S. Pat. No. 4,744,834. The
use of chelating and complexing agents to sequester metals in
various cleaners has also been reported in WO 9705228, U.S. Pat.
Nos. 5,466,389, 5,498,293, EP 812011, U.S. Pat. No. 5,561,105, JP
06216098, JP 0641773, JP 06250400 and GB 1,573,206.
The use of an alkyl ammonium hydroxide solution containing a
surfactant capable of forming a monolayer absorbed onto the
sidewall of a patterned metal layer is disclosed in U.S. Pat. No.
6,057,240 for use as a post etch residue remover used in the
fabrication process of a microelectonic device.
Photoresist developers containing tetramethylammonium hydroxide
have also been disclosed as being useful for removing post via etch
polymers in U.S. Pat. Nos. 5,412,868; 5,597,983 and EP 540261
B1.
U.S. Pat. No. 5,466,389 discloses an aqueous alkaline containing
cleaning solution for microelectronics substrates that contains a
quaternary ammonium hydroxide and optional metal chelating agents
and is useful for a pH range of about 8 to 10. In the present
invention, a pH greater than 10 is required to effect the desired
residue removal.
U.S. Pat. No. 5,498,293 discloses a process for using an aqueous
alkaline cleaning solution that contains a quaternary ammonium
hydroxide and optional metal chelating agents useful for cleaning
silicon wafers. The disclosure of this cleaning process is for
treatments to substrates before the presence of integrated metal
circuits and is used to generate a wafer surface that is
essentially silicon dioxide free and would be employed before the
use of photoresist for integrated circuit fabrication. The present
invention, in contrast, focuses on the cleaning of wafers with
integrated circuits present which have been photoresist coated,
etched, and oxygen plasma ashed.
Although the compositions disclosed in WO 9960448 effectively
remove all organic contamination and metal-containing residues
remaining after a typical etching process, these compositions have
a relatively short bath life. There is, therefore, a need for
similar compositions with very long bath lives exceeding twenty
hours.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide
compositions useful in the microelectronics industry for cleaning
semiconductor wafer substrates.
It is another object of the present invention to provide
compositions that remove metallic and organic contamination from
semiconductor wafer substrates without damaging the integrated
circuits.
It is another object of the present invention to provide
compositions that have very long effective bath lives.
It is a further object of the present invention to provide a method
for cleaning semiconductor wafer substrates that removes metallic
and organic contamination from such substrates without damaging the
integrated circuits and avoiding the expense and adverse
consequences caused by intermediate rinses.
These and other objects are achieved using new aqueous compositions
for stripping or cleaning semiconductor wafer substrates that
contain one or more metal ion-free bases and at least one bath
stabilizing agent. The compositions are placed in contact with a
semiconductor wafer substrate for a time and at a temperature
sufficient to clean unwanted contaminants and/or residues from the
substrate surface.
Preferably, the compositions contain one or more metal ion-free
bases dissolved in water in sufficient amounts to produce a pH of
about 10 or greater and a bath stabilizing effective amount,
generally about 0.1% to about 50% by weight, of at least one bath
stabilizing agent comprising at least one compound with at least
one pKa in the range of 10 to 13.
Any suitable base may be used in the compositions of this
invention. Preferably, the base is selected from hydroxides and
organic amines, most preferably quaternary ammonium hydroxides,
ammonium hydroxides and diamines.
Any suitable bath stabilizing agent comprising of at least one pKa
in the range of 10 to 13 may be used in the compositions of the
present invention. The bath stabilizing agents are preferably
compounds with at least one pKa in the range of 11 to 12.5. The
most preferable of these compounds are acetone oxime, hydrogen
peroxide, salicylic acid, 5-sulfosalicylic acid, phosphoric acid,
2-hydroxypyridine, 4-hydroxypyridine, resorcinol,
2-methylresorcinol, salicylaldoxime, 2-methyl-1,5-pentanediamine,
1,2-ethanediamine, 1,3-propanediamine, 1,4-butanediamine,
1,5-pentanediamine, 1,6-hexanediamine, 1,7-heptanediamine,
1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine,
1,11-undecanediamine, 1,12-dodecanediamine, 1,3-diaminopentane and
orcinol. Other examples of bath stabilizing agents with a pKa in
the preferred range of 11 to 12.5 are: hydrogen germanate,
adenosine, cytosine, arginine, benzil-.alpha.-dioxime,
benzimidazole, benzoylhydrazine, benzoylpyruvic acid, berberine,
biguanide, 2-butyl-1-methyl-2-pyrroline, calmagite, chrome azurol
S, chrome dark blue, cumene hydroperoxide,
1,2-cyclohexylenedinitriloacetic acid, cytidine, diethylbiguanide,
diguanide, 2,4-dihydroxy-1-phenylazobenzene, 2,6-dihydroxypurine,
dimethylbiguanide, ethylbiguanide, ethylenebiguanide, ethyl methyl
ketoxime, 1-ethyl-2-methyl-2-pyrroline, 4-formyl-3-methoxypyridine,
guanine, guanosine, 2-hydroxybenzaldehyde oxime,
N-(hydroxyethyl)biguanide, 2-hydroxyquinoline, hypoxanthene,
inosine, 5-iodohistamine, 2,2'-methylenebis(4-chlorophenol),
2-methyl-8-hydroxyquinoline, 4-methyl-8-hydroxyquinoline,
1-methylxanthine, phenylalanylarginine, silicic acid, sparteine,
thorin, toluhydroquinone, tyrosylarginine, xanthosine, acetamidine,
trifluoroethanol, trichloroethanol, pyridine-4-aldehyde,
hypoxanthine, uric acid, pyrrolidine, diethylamine, piperidine,
3-amino-3-methylpentane, diisopropylamine, saccharin,
2,2,4-trimethylpiperidine, dibutylamine,
L-3,4-dihydroxyphenylalanine, 2,2,6,6-tetramethylpiperidine,
5-hydroxytryptamine, butylcyclohexylamine, 2-phenylbenzimidazole,
2-methyl-2-butanethiol, 2-methyl-2-propanethiol, dihexylamine,
methoxypyridine, 1,4-dihydroxy-2,3,5,6-tetramethylbenzene,
glutarimide, malanonitrile, benzamidine, 4-hydroxyquinoline,
4,4,9,9-tetramethyl-5,8-diazododecane-2,11-diamine,
1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine,
1,9-nonanediamine 1,10-decanediamine, 1,12-dodecanediamine,
hydrogen hyponitrite, hydroxylamine-N,N-disulfonic acid,
(1,2-cyclohexylenedinitrilo)tetraacetic acid (CYDTA) and
diethylenetriaminepenta(methylenephosphonic acid) (DETPA).
Additional examples of bath stabilizing agents with at least one
pKa in the 10-11 range are: lysine, tyrosine,
3-amino-N,N-bis(2-aminoethyl)propylamine, tris(2-aminoethyl)amine,
3-(cyclohexylamino)-1-propanesulfonic acid, methylamine,
dimethylamine, ethylamine, cysteamine, 1,2-ethanediamine,
.alpha.-alanine, .beta.-alanine, azetidine, methyiglycine,
cysteine, propylamine, 1,3-propanediamine, 4-aminobutanoic acid,
2-methylalanine, homocysteine, 2,4-diaminobutanoic acid,
butylamine, 1,4-butanediamine, 2,3-butanediamine,
1,2-dimethylaminoethane, proline, N-methylpyrrolidine,
5-aminopentanoic acid, N-propylglycine, ornithine,
1-amino-2,2-dimethylpropane, diethylmethylamine,
3-methyl-1-butanamine, 2-methyl-2-butanamine, 3-pentanamine,
pentylamine, 1,5-pentanediamine, 2-pyridinecarboxaldehyde oxime,
hydroquinone, pipecolic acid, cyclohexylamine,
1,2-dimethylpyrrolidine, 1-methylpiperidine, 6-aminohexanoic acid,
hexylamine, triethylamine, cresol, 2-dimethylaminopurine,
1,2-dimethylpiperidine, 1-ethylpiperidine, 2-heptanamine,
heptylamine, tyramine, dopamine, N-methyl-2-heptanamine,
octylamine, 1-butylpiperidine, nonylamine, tryptamine, d-ephedrine,
bornylamine, neobornylamine, decylamine, undecylamine,
dodecylamine, tridecylamine, tetradecylamine, L-thyroxine,
pentadecylamine, hexadecylamine, octadecylamine, 4-aminobutyric
acid, 2-amino-2-methylpropionic acid, 3-aminopropionic acid,
ethylenediaminetetraacetic acid (EDTA),
N,N'-dimethylethyleneamine-N,N'-diacetic acid, methylaminodiacetic
acid, 2-methyl-2-propylamine, nitrilotriacetic acid,
1,2,4-triazole, chloral, ethtyl acetoacetate, phenol,
.beta.-phenylethylboric acid, nitromethane, thioglycollic acid,
ethyl mercaptan, cyanamide, docosylamine, tert-butylamine,
trimethylamine, 2-mercaptoethylamine, 5-aminovaleric acid,
4-aminophenol, hydrogen hypoiodite, aminopropylmorpholine,
ethanethiol, carbonic acid, tetramethylammonium carbonate, ammonium
bicarbonate, ammonium carbonate, choline bicarbonate, carbon
dioxide+water, threonine, hydrogen thiophosphate, sarcosine,
4-methoxyphenol, 4-ethoxyphenol, 4-propoxyphenol, 4-butoxyphenol
and 4-pentoxyphenol.
Additional examples of bath stabilizing agents with at least one
pKa in the 12.5-13 range are: 5-hydroxymethylcytosine, oxaloacetic
acid, cumene hydroperoxide, diguanidine, hydrogen sulfide and
hydrogen peroxophosphate.
The compositions of the present invention may contain other
components such as silicates, chelating agents, organic
co-solvents, and surfactants. Chelating agents are preferably
present in amounts up to about 2% by weight, organic co-solvents
are preferably present in amounts up to about 30% by weight. The
compositions can be used to clean substrates containing integrated
circuits or can be used to clean substrates that do not contain
integrated circuits. When integrated circuits are present, the
composition removes the contaminants without damaging the
integrated circuits.
The method for cleaning semiconductor wafer substrates of the
present invention requires that the compositions of the present
invention be placed in contact with a semiconductor wafer substrate
for a time and at a temperature sufficient to clean unwanted
contaminants and/or residues from the substrate surface. The method
includes both bath and spray applications. Typically, the substrate
is exposed to the composition for the appropriate time and at the
appropriate temperature, rinsed using high purity de-ionized water,
and dried.
The compositions clean wafer substrates by removing metallic and
organic contamination. Importantly, the cleaning process does not
damage integrated circuits on the wafer substrates and avoids the
expense and adverse consequences associated with intermediate
rinses required in prior methods.
Other objects, advantages, and novel features of the present
invention will become apparent in the following detailed
description of the invention.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides new aqueous compositions for
stripping or cleaning semiconductor wafer substrates that contain
one or more metal ion-free bases and one or more bath stabilizing
agents comprising a compound with at least one pKa in the range of
10-13. Preferably, the invention provides aqueous, alkaline
stripping or cleaning compositions comprising one or more alkaline
metal ion-free base components in an amount sufficient to produce a
solution pH of about 10 or greater, preferably from about pH 11 to
about pH 13, and one or more bath stabilizing agents comprising a
compound with at least one pKa in the range of 10-13, preferably
11-12.5, in a concentration by weight of about 0.1% to about 50%,
preferably from about 0.1% to about 35%. In formulations that
contain more than about 30% total organics, the pH of the solution
should be taken for a 5 wt % solution diluted in de-ionized
water.
The compositions may also contain a water-soluble metal ion-free
silicate in a concentration by weight of about 0.01% to 5%, and a
chelating agent in a concentration by weight of about 0.01% to
about 10%, generally from about 0.01% to about 2%. Further optional
components are water-soluble organic solvents in a concentration by
weight of about 0.1% to about 30%, preferably about 1% to about
30%, and a water-soluble surfactant in an amount by weight of about
0.01% to about 1%, preferably about 0.01% to about 0.5%.
The composition is an aqueous solution containing the base, the
bath stabilizing agent, the optional components, if any, and water,
preferably high purity de-ionized water.
Any suitable base may be used in the compositions of the present
invention. The bases are preferably quaternary ammonium hydroxides,
such as tetraalkyl ammonium hydroxides (including hydroxy- and
alkoxy-containing alkyl groups generally of from 1 to 4 carbon
atoms in the alkyl or alkoxy group) and diamines. The most
preferable of these alkaline materials are tetramethyl ammonium
hydroxide and trimethyl-2-hydroxyethyl ammonium hydroxide
(choline). Examples of other usable quaternary ammonium hydroxides
include: trimethyl-3-hydroxypropyl ammonium hydroxide,
trimethyl-3-hydroxybutyl ammonium hydroxide,
trimethyl-4-hydroxybutyl ammonium hydroxide,
triethyl-2-hydroxyethyl ammonium hydroxide,
tripropyl-2-hydroxyethyl ammonium hydroxide,
tributyl-2-hydroxyethyl ammonium hydroxide,
dimethylethyl-2-hydroxyethyl ammonium hydroxide,
dimethyldi(2-hydroxyethyl) ammonium hydroxide, monomethyltriethanol
ammonium hydroxide, tetraethyl ammonium hydroxide, tetrapropyl
ammonium hydroxide, tetrabutyl ammonium hydroxide, tetraethanol
ammonium hydroxide, monomethyltriethyl ammonium hydroxide,
monomethyltripropyl ammonium hydroxide, monomethyltributyl ammonium
hydroxide, monoethyltrimethyl ammonium hydroxide, monoethyltributyl
ammonium hydroxide, dimethyldiethyl ammonium hydroxide,
dimethyldibutyl ammonium hydroxide, and the like and mixtures
thereof.
Other bases that will function in the present invention include
ammonium hydroxide, organic amines particularly alkanolamines such
as 2-aminoethanol, 1-amino-2-propanol, 1-amino-3-propanol,
2-(2-aminoethoxy)ethanol, 2-(2-aminoethylamino)ethanol,
2-(2-aminoethylamino)ethylamine and the like, and other strong
organic bases such as guanidine, 1,2-ethanediamine,
1,3-propanediamine, 1,4-butanediamine, 1,5-pentanediamine,
1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine,
1,9-nonanediamine, 1,10-decanediamine, 1,12-dodecanediamine,
1,3-pentanediamine, 4-aminomethyl-1,8-octanediamine,
aminoethylpiperazine, 4-(3-aminopropyl)morpholine,
1,2-diaminocyclohexane, tris(2-aminoethyl)amine,
2-methyl-1,5-pentanediamine and hydroxylamine. Alkaline solutions
containing metal ions such as sodium or potassium may also be
operative, but are not preferred because of the possible residual
metal contamination that could occur. Mixtures of these additional
alkaline components, particularly ammonium hydroxide, with the
aforementioned tetraalkyl ammonium hydroxides are also useful.
Any suitable bath stabilizing agent comprising a compound having at
least one pKa in the range of 10 to 13, may be used in the
compositions of the present invention. The bath stabilizing agents
are preferably compounds with at least one pKa in the range of 11
to 12.5. The most preferable of these compounds are acetone oxime,
hydrogen peroxide, salicylic acid, 5-sulfosalicylic acid,
phosphoric acid, 2-hydroxypyridine, 4-hydroxypyridine, resorcinol,
2-methylresorcinol, salicylaldoxime, 2-methyl-1,5-pentanediamine,
1,2-ethanediamine, 1,3-propanediamine, 1,4-butanediamine,
1,6-hexanediamine, 1,8-octanediamine, 1,12-dodecanediamine,
1,3-diaminopentane and orcinol, but are not limited to, those
listed herein before in the Summary Of the Invention section.
Additional suitable bath stabilizing agents having at least one pKa
value of from 10 to 13 can be found listed in "Lange's Handbook of
Chemistry", 15.sup.th Edition, Section 8, pages 8-24 to 8-79, by J.
Dean, "The Determination of Ionization Constants, A Laboratory
Manual" by A. Albert and E. Serjeant, 2nd edition, Chapters 6 to 9,
pages 72-107, and the "CRC Handbook of Chemistry and Physics",
78.sup.th Edition, pages 7-1 to 7-3, 7-6 and 8-43 to 8-55, by D.
Lide. Additional compounds with at least one pKa in the 10-13 range
can also be found in the computer software programs "NIST Standard
Reference Database 46: NIST Critically Selected Stability Constants
of metal Complexes Database" available from NIST and the program
"ACD/pKa DB" that is available from Advanced Chemistry Development,
Inc. of Toronto, Canada. ACD/pKa DB also allows predictions of
pKa's from structures. The compounds having at least one pKa in the
range of 10-13 useful as bath stabilization agents for this
invention are those that when incorporated into a composition for
stripping or cleaning integrated circuit substrates provide
compositions that evidence less pH drop on aging of the composition
compared to an identical composition without the bath stabilization
agent. Mixtures of suitable bath stabilizing agents may be
used.
Any suitable metal ion-free silicate may be used in the
compositions of the present invention. The silicates are preferably
quaternary ammonium silicates, such as tetraalkyl ammonium silicate
(including hydroxy- and alkoxy-containing alkyl groups generally of
from 1 to 4 carbon atoms in the alkyl or alkoxy group). The most
preferable metal ion-free silicate component is tetramethyl
ammonium silicate. Other suitable metal ion-free silicate sources
for this invention may be generated in-situ by dissolving any one
or more of the following materials in the highly alkaline cleaner.
Suitable metal ion-free materials useful for generating silicates
in the cleaner are solid silicon wafers, silicic acid, colloidal
silica, fumed silica or any other suitable form of silicon or
silica. Metal silicates such as sodium metasilicate may be used but
are not recommended due to the detrimental effects of metallic
contamination on integrated circuits.
The compositions of the present invention may also be formulated
with suitable metal chelating or complexing agents to increase the
capacity of the formulation to retain metals in solution and to
enhance the dissolution of metallic residues on the wafer
substrate. Typical examples of chelating agents useful for this
purpose are the following organic acids and their isomers and
salts: (ethylenedinitrilo)tetraacetic acid (EDTA),
butylenediaminetetraacetic acid,
(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA),
diethylenetriaminepentaacetic acid, ethylenediaminetetrapropionic
acid, (hydroxyethyl)ethylenediaminetriacetic acid (HEDTA),
N,N,N',N'-ethylenediaminetetra(methylenephosphonic)acid (EDTMP),
triethylenetetraminehexaacetic acid (TTHA),
1,3-diamino-2-hydroxypropane-N,N,N',N'-tetraacetic acid (DHPTA),
methyliminodiacetic acid, propylenediaminetetraacetic acid,
1,5,9-triazacyclododecane-N,N',N"-tris(methylenephosphonic acid)
(DOTRP),
1,4,7,10-tetraazacyclododecane-N,N',N",N'"-tetrakis(methylenephosphonic
acid) (DOTP), nitrilotris(methylene)triphosphonic acid,
diethylenetriaminepenta(methylenephosphonic acid) (DETAP),
aminotri(methylenephosphonic acid),
1-hydroxyethylene-1,1-diphosphonic acid, bis(hexamethylene)triamine
phosphonic acid,
1,4,7-triazacyclononane-N,N',N"-tris(methylenephosphonic acid
(NOTP), 2-phosphonobutane-1,2,4-tricarboxylic acid,
nitrolotriacetic acid (NTA), citric acid, tartaric acid, gluconic
acid, saccharic acid, glyceric acid, oxalic acid, phthalic acid,
maleic acid, mandelic acid, malonic acid, lactic acid, salicylic
acid, 5-sulfosalicylic acid, catechol, gallic acid, propyl gallate,
pyrogallol, 8-hydroxyquinoline, and cysteine. Examples of
complexing agents are phosphoric acid, nitric acid, sulfuric acid,
hydrochloric acid and hydrofluoric acid. A phosphonic acid or CyDTA
chelating agent is preferably employed when the composition
contains an oxidizing bath stabilizing agent, such as hydrogen
peroxide. Chelating agents such as EDTA are not nearly as oxidation
resistant as CyDTA and phosphonic acid chelating agents.
Preferred chelating agents are aminocarboxylic acids such as EDTA
or CyDTA and phosphonic acids. Many aminocarboxylic acids and
phosphonic acid chelating agents have at least one pKa in the 10-13
range. Chelating agents of this class have a high affinity for the
aluminum-containing residues typically found on metal lines and
vias after plasma "ashing". In addition, the pKa's for this class
of chelating agents typically include one pKa of approximately 12
which improves the performance of the compositions of the
invention.
The compositions of the present invention may also contain one or
more suitable water-soluble organic solvents. Among the various
organic solvents suitable are alcohols, polyhydroxy alcohols,
glycols, glycol ethers, alkyl-pyrrolidinones such as
N-methylpyrrolidinone (NMP), 1-hydroxyalkyl-2-pyrrolidinones such
as 1-(2-hydroxyethyl)-2-pyrrolidinone (HEP), dimethylformamide
(DMF), dimethylacetamide (DMAc), sulfolane, dimethyl-2-piperidone
(DMPD) or dimethylsulfoxide (DMSO). These solvents may be added to
reduce aluminum and/or aluminum-copper alloy and/or copper
corrosion rates if further aluminum and/or aluminum-copper alloy
and/or copper corrosion inhibition is desired. Preferred
water-soluble organic solvents are polyhydroxy alcohols such as
glycerol and/or 1-hydroxyalkyl-2-pyrrolidinones such as
1-(2-hydroxyethyl)-2-pyrrolidinone (HEP).
The compositions of the present invention may also contain any
suitable water-soluble amphoteric, non-ionic, cationic or anionic
surfactant. The addition of a surfactant will reduce the surface
tension of the formulation and improve the wetting of the surface
to be cleaned and therefore improve the cleaning action of the
composition. The surfactant may also be added to reduce aluminum
corrosion rates if further aluminum corrosion inhibition is
desired.
Amphoteric surfactants useful in the compositions of the present
invention include betaines and sulfobetaines such as alkyl
betaines, amidoalkyl betaines, alkyl sulfobetaines and amidoalkyl
sulfobetaines; aminocarboxylic acid derivatives such as
amphoglycinates, amphopropionates, amphodiglycinates, and
amphodipropionates; iminodiacids such as alkoxyalkyl iminodiacids
or alkoxyalkyl iminodiacids; amine oxides such as alkyl amine
oxides and alkylamido alkylamine oxides; fluoroalkyl sulfonates and
fluorinated alkyl amphoterics; and mixtures thereof.
Preferably, the amphoteric surfactants are cocoamidopropyl betaine,
cocoamidopropyl dimethyl betaine, cocoamidopropyl hydroxy sultaine,
capryloamphodipropionate, cocoamidodipropionate,
cocoamphopropionate, cocoamphohydroxyethyl propionate,
isodecyloxypropylimino dipropionic acid, laurylimino dipropionate,
cocoamidopropylamine oxide and cocoamine oxide and fluorinated
alkyl amphoterics.
Non-ionic surfactants useful in the compositions of the present
invention include acetylenic diols, ethoxylated acetylenic diols,
fluorinated alkyl alkoxylates, fluorinated alkylesters, fluorinated
polyoxyethylene alkanols, aliphatic acid esters of polyhydric
alcohols, polyoxyethylene monoalkyl ethers, polyoxyethylene diols,
siloxane type surfactants, and alkylene glycol monoalkyl ethers.
Preferably, the non-ionic surfactants are acetylenic diols or
ethoxylated acetylenic diols.
Anionic surfactants useful in the compositions of the present
invention include carboxylates, N-acylsarcosinates, sulfonates,
sulfates, and mono and diesters of orthophosphoric acid such as
decyl phosphate. Preferably, the anionic surfactants are metal-free
surfactants.
Cationic surfactants useful in the compositions of the present
invention include amine ethoxylates, dialkyldimethylammonium salts,
dialkylmorpholinum salts, alkylbenzyldimethylammonium salts,
alkyltrimethylammonium salts, and alkylpyridinium salts.
Preferably, the cationic surfactants are halogen-free
surfactants.
In a preferred embodiment of the present invention, the composition
is an aqueous solution containing about 0.1-25%, more preferably
about 0.1-12%, by weight tetramethylammonium hydroxide (TMAH) and
about 0.1% to about 35% by weight sulfosalicylic acid, phosphoric
acid, hydrogen peroxide, 2-hydroxypyridine, 4-hydroxypyridine,
resorcinol or 2-methylresircinol.
In another embodiment of the present invention, the composition is
an aqueous solution containing about 0.1-5% by weight
tetramethylammonium hydroxide (TMAH), about 0.1% to about 3% by
weight sulfosalicylic acid or phosphoric acid, about 0.01-1% by
weight trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA),
and about 0-1% by weight (calculated as % SiO.sub.2)
tetramethylammonium silicate (TMAS).
In another embodiment of the present invention, the composition is
an aqueous solution containing about 0.1-5% by weight
tetramethylammonium hydroxide (TMAH), about 0.01-1% by weight
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), about
0.1% to about 3% by weight sulfosalicylic acid or phosphoric acid,
about 0-1% by weight (calculated as % SiO.sub.2)
tetramethylammonium silicate (TMAS), and about 0.5-30% by weight of
polyhydroxy compounds, preferably glycerol.
In another embodiment of the present invention, the composition is
an aqueous solution containing about 0.1-3% by weight
tetramethylammonium hydroxide (TMAH), about 0.1% to about 3% by
weight sulfosalicylic acid or phosphoric acid, about 0.01-1% by
weight trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA),
about 0-1% by weight (calculated as % SiO.sub.2)
tetramethylammonium silicate (TMAS), about 0.5-30% by weight of
polyhydroxy compounds, and about 0.01-0.3% by weight of a nonionic
ethoxylated acetylenic diol surfactant.
In another embodiment of the present invention, the composition is
an aqueous solution containing about 0.1-5% by weight
tetramethylammonium hydroxide (TMAH), about 0.1% to about 3% by
weight hydrogen peroxide or salicylic acid, about 0.01-1% by weight
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), and
about 0-1% by weight (calculated as % SiO.sub.2)
tetramethylammonium silicate (TMAS).
In another embodiment of the present invention, the composition is
an aqueous solution containing about 0.1-5% by weight
tetramethylammonium hydroxide (TMAH), about 0.01-1% by weight
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), about
0.1% to about 3% by weight hydrogen peroxide or salicylic acid,
about 0-1% by weight (calculated as % SiO.sub.2)
tetramethylammonium silicate (TMAS), and about 0.5-30% by weight of
polyhydroxy compounds, preferably glycerol.
In another embodiment of the present invention, the composition is
an aqueous solution containing about 0.1-3% by weight
tetramethylammonium hydroxide (TMAH), about 0.1% to about 3% by
weight hydrogen peroxide or salicylic acid, about 0.01-1% by weight
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), about
0-1% by weight (calculated as % SiO.sub.2) tetramethylammonium
silicate (TMAS), about 0.5-30% by weight of polyhydroxy compounds,
and about 0.01-0.3% by weight of a nonionic ethoxylated acetylenic
diol surfactant.
In another embodiment of the present invention, the composition is
an aqueous solution containing about 0.1-2% by weight
tetramethylammonium hydroxide (TMAH), about 0.01-1% by weight
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), about
0-1% by weight (calculated as % SiO.sub.2) tetramethylammonium
silicate (TMAS), about 0.1% to about 3% by weight hydrogen peroxide
or salicylic acid and about 0.5-30% by weight of an
alkyl-pyrrolidinone such as 1-(2-hydroxyethyl)-2-pyrrolidinone
(HEP), preferably 1-(2-hydroxyethyl)-2-pyrrolidinone (HEP).
In another embodiment of the present invention, the composition is
an aqueous solution containing about 0.1-2% by weight
tetramethylammonium hydroxide (TMAH), about 0.01-1% by weight
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), about
0-1% by weight (calculated as % SiO.sub.2) tetramethylammonium
silicate (TMAS), about 0.1% to about 3% by weight hydrogen peroxide
or salicylic acid, about 0.5-30% by weight of an
alkyl-pyrrolidinone such as 1-(2-hydroxyethyl)-2-pyrrolidinone
(HEP), and about 0.01-0.3% by weight of a nonionic ethoxylated
acetylenic diol surfactant.
In another embodiment of the present invention, the composition is
an aqueous solution containing about 0.1-2% by weight
tetramethylammonium hydroxide (TMAH), about 0.01-1% by weight
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), about
0.1% to about 3% by weight sulfosalicylic acid or phosphoric acid,
about 0-1% by weight (calculated as % SiO.sub.2)
tetramethylammonium silicate (TMAS), and about 0.5-30% by weight of
an alkyl-pyrrolidinone such as 1-(2-hydroxyethyl)-2-pyrrolidinone
(HEP), preferably 1-(2-hydroxyethyl)-2-pyrrolidinone (HEP).
In another embodiment of the present invention, the composition is
an aqueous solution containing about 0.1-2% by weight
tetramethylammonium hydroxide (TMAH), about 0.01-1% by weight
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), about
0.1% to about 3% by weight sulfosalicylic acid or phosphoric acid,
about 0-1% by weight (calculated as % SiO.sub.2)
tetramethylammonium silicate (TMAS), about 0.5-30% by weight of an
alkyl-pyrrolidinone such as 1-(2-hydroxyethyl)-2-pyrrolidinone
(HEP), and about 0.01-0.3% by weight of a nonionic ethoxylated
acetylenic diol surfactant.
In another embodiment of the present invention, the composition is
an aqueous solution containing about 0.1-5% by weight
tetramethylammonium hydroxide (TMAH), about 0.01-1% by weight
diethylenetriaminepenta(methylenephosphonic acid), about 0.1% to
about 3% by weight hydrogen peroxide and about 0-1% by weight
(calculated as % SiO.sub.2) tetramethylammonium silicate
(TMAS).
In another embodiment of the present invention, the composition is
an aqueous solution containing about 0.1-25% by weight
tetramethylammonium hydroxide (TMAH), about 0.1% to about 20% by
weight hydroxylamine, about 0.1% to about 35% by weight
2-hydroxypyridine or 4-hydroxypyridine, about 0-1% by weight
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), about
0-1% by weight (calculated as % SiO.sub.2) tetramethylammonium
silicate (TMAS) and about 0-0.3% by weight of a nonionic
ethoxylated acetylenic diol surfactant.
In another embodiment of the present invention, the composition is
an aqueous solution containing about 0.1-10% by weight
tetramethylammonium hydroxide (TMAH), about 0.1% to about 15% by
weight 2-hydroxypyridine, about 0-1% by weight
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), about
0-1% by weight (calculated as % SiO.sub.2) tetramethylammonium
silicate (TMAS), about 0-30% by weight of polyhydroxy compounds,
and about 0-0.3% by weight of a nonionic ethoxylated acetylenic
diol surfactant.
In another embodiment of the present invention, the composition is
an aqueous solution containing about 0.1-10% by weight
tetramethylammonium hydroxide (TMAH), about 0.1% to about 15% by
weight 4-hydroxypyridine, about 0-1% by weight
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), about
0-1% by weight (calculated as % SiO.sub.2) tetramethylammonium
silicate (TMAS), about 0-30% by weight of polyhydroxy compounds,
and about 0-0.3% by weight of a nonionic ethoxylated acetylenic
diol surfactant.
In another embodiment of the present invention, the composition is
an aqueous solution containing about 0.1-25% by weight
tetramethylammonium hydroxide (TMAH), about 0.1% to about 15% by
weight resorcinol, about 0-1% by weight
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), about
0-2% by weight (calculated as % SiO.sub.2) tetramethylammonium
silicate (TMAS), about 0-30% by weight of polyhydroxy compounds,
and about 0-0.3% by weight of a nonionic ethoxylated acetylenic
diol surfactant.
In another embodiment of the present invention, the composition is
an aqueous solution containing about 0.1-4% by weight
tetramethylammonium hydroxide (TMAH), about 0.1% to about 4% by
weight 2-methylresorcinol, about 0-1% by weight
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), about
0-2% by weight (calculated as % SiO.sub.2) tetramethylammonium
silicate (TMAS), about 0-30% by weight of polyhydroxy compounds,
and about 0-0.3% by weight of a nonionic ethoxylated acetylenic
diol surfactant.
In another embodiment of the present invention, the composition is
an aqueous solution containing about 0.1-4% by weight
tetramethylammonium hydroxide (TMAH), about 0.1% to about 4% by
weight orcinol, about 0-1% by weight
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), about
0-2% by weight (calculated as % SiO.sub.2) tetramethylammonium
silicate (TMAS), about 0-30% by weight of polyhydroxy compounds,
and about 0-0.3% by weight of a nonionic ethoxylated acetylenic
diol surfactant.
In another embodiment of the present invention, the composition is
an aqueous solution containing about 0.1-10% by weight
tetramethylammonium hydroxide (TMAH), about 0.1% to about 15% by
weight 2-hydroxypyridine, about 0-1% by weight (calculated as %
SiO.sub.2) tetramethylammonium silicate (TMAS), about 0-30% by
weight of polyhydroxy compounds, and about 0-0.3% by weight of a
nonionic ethoxylated acetylenic diol surfactant.
In another embodiment of the present invention, the composition is
an aqueous solution containing about 0.1-10% by weight
tetramethylammonium hydroxide (TMAH), about 0.1% to about 15% by
weight 4-hydroxypyridine, about 0-1% by weight (calculated as %
SiO.sub.2) tetramethylammonium silicate (TMAS), about 0-30% by
weight of polyhydroxy compounds, and about 0-0.3% by weight of a
nonionic ethoxylated acetylenic diol surfactant.
In another embodiment of the present invention, the composition is
an aqueous solution containing about 0.1-10% by weight
tetramethylammonium hydroxide (TMAH), about 0.1% to about 15% by
weight 2-hydroxypyridine, about 0-1% by weight (calculated as %
SiO.sub.2) tetramethylammonium silicate (TMAS) and about 0-30% by
weight of polyhydroxy compounds.
In another embodiment of the present invention, the composition is
an aqueous solution containing about 0.1-10% by weight
tetramethylammonium hydroxide (TMAH), about 0.1% to about 15% by
weight 4-hydroxypyridine, about 0-1% by weight (calculated as %
SiO.sub.2) tetramethylammonium silicate (TMAS) and about 0-30% by
weight of polyhydroxy compounds.
In all the embodiments, the balance of the composition is made up
with water, preferably high purity de-ionized water.
The method of the present invention cleans semiconductor wafer
substrates by exposing the contaminated substrate to the
compositions of the present invention for a time and at a
temperature sufficient to clean unwanted contaminants from the
substrate surface. Optionally, the substrate is rinsed to remove
the composition and the contaminants and dried to remove any excess
solvents or rinsing agents. The substrate can then be used for its
intended purpose.
Preferably, the method uses a bath or spray application to expose
the substrate to the composition. Bath or spray cleaning times are
generally 1 minute to 30 minutes, preferably 5 minutes to 20
minutes. Bath or spray cleaning temperatures are generally
10.degree. C. to 85.degree. C., preferably 20.degree. C. to
65.degree. C.
If required, the rinse times are generally 10 seconds to 5 minutes
at room temperature, preferably 30 seconds to 2 minutes at room
temperature. Preferably de-ionized water is used to rinse the
substrates.
If required, drying the substrate can be accomplished using any
combination of air-evaporation, heat, spinning, or pressurized gas.
The preferred drying technique is spinning under a filtered inert
gas flow, such as nitrogen, for a period of time until the wafer
substrate is dry.
The method of the present invention is very effective for cleaning
semiconductor wafer substrates that have been previously oxygen
plasma ashed to remove bulk photoresist, particularly wafer
substrates containing a silicon, silicon oxide, silicon nitride,
tungsten, tungsten alloy, titanium, titanium alloy, tantalum,
tantalum alloy, copper, copper alloy, aluminum or aluminum alloy
film. The method removes unwanted metallic and organic contaminants
but does not cause unacceptable corrosion to the silicon, silicon
oxide, silicon nitride, tungsten, tungsten alloy, titanium,
titanium alloy, tantalum, tantalum alloy, copper, copper alloy,
aluminum or aluminum alloy film.
The following examples illustrate the specific embodiment of the
invention described in this document. As would be apparent to
skilled artisans, various changes and modifications are possible
and are contemplated within the scope of the invention
described.
EXAMPLES
The percentages given in the examples are by weight unless
specified otherwise. The amount of aluminum or aluminum-copper
alloy metal corrosion is expressed as both percent metal loss and
as a general corrosion remark. The general corrosion remarks given
are very slight, slight, light, moderate and severe. A small amount
of metal corrosion that was considered to be within acceptable
limits were assigned very slight or slight. Light, moderate or
severe corrosion were considered to be unacceptable. All cleaning
and corrosion data entries generated using a Field Emission
Scanning Electron Microscope (FE-SEM) were based on a visual
interpretation of differences between untreated and treated samples
from the same wafer.
The small beaker aging tests were conducted in 100 ml or 150 ml
uncovered glass beakers placed in a chemical fume hood for 16 or 20
hours at room temperature without stirring. Large beaker aging
tests were conducted in uncovered 4-liter (4 L) glass beakers
placed in a chemical fume hood with stirring done at a rate of 150
RPM using a magnetic stir-bar for 12 to 29 hours. The 4-liter
beaker aging tests were all conducted at temperatures above room
temperature (noted in the tables below). A portion of the same
unaged batch of solution was also kept in a sealed poly bottle for
comparison. At the completion of the aging tests the solutions were
placed into poly bottles then sealed for later pH comparison
measurements. In Examples 1 to 3 and Example 11, pH measurement
shown were done using a glass combination electrode standardized
with pH 4 and pH 10 buffers. In Examples 4 to 10, pH measurements
shown were done using a glass combination electrode standardized
with pH 7 and pH 10 buffers. The pH meter was re-standardized after
the completion of one set of unaged/aged solutions (maximum of two
solutions per standardization) to ensure accurate pH comparison
measurements.
The pKa values shown in the tables below were primarily obtained
from the "Lange's Handbook of Chemistry", 15.sup.th Edition,
Section 8, pages 8-24 to 8-79, by J. Dean, "The Determination of
Ionization Constants, A Laboratory Manual" by A. Albert and E.
Serjeant, 2nd edition, Chapters 6 to 9, pages 72-107, and the "CRC
Handbook of Chemistry and Physics", 78.sup.th Edition, pages 7-1 to
7-3, 7-6 and 8-43 to 8-55, by D. Lide. All pka's shown are for room
temperature (18-25.degree. C.).
Example 1
Aqueous solution "A1" was prepared with 2.4 weight percent
tetramethylammonium hydroxide (TMAH), 0.1 weight percent
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), 0.06
weight percent of the non-ionic surfactant Surfynol-465 (a product
of Air Products and Chemicals, Inc.), 0.9 weight percent glacial
acetic acid, 3.0 weight percent glycerol and 0.9 weight percent
salicylic acid (remainder of this solution being made up with
de-ionized water) and has a pH of about 12.5.
Aqueous solution "A2" was prepared with 3.2 weight percent
tetramethylammonium hydroxide (TMAH), 0.1 weight percent
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), 0.06
weight percent of the non-ionic surfactant Surfynol-465 (a product
of Air Products and Chemicals, Inc.), 0.9 weight percent glacial
acetic acid, 3.0 weight percent glycerol and 2.2 weight percent
salicylic acid (remainder of this solution being made up with
de-ionized water) and has a pH of about 12.5.
Aqueous solution "A3" was prepared with 1.0 weight percent
tetramethylammonium hydroxide (TMAH), 0.1 weight percent
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), 0.06
weight percent of the non-ionic surfactant Surfynol-465 (a product
of Air Products and Chemicals, Inc.), 3.0 weight percent glycerol
and 0.9 weight percent salicylic acid (remainder of this solution
being made up with de-ionized water) and has a pH of about
12.5.
Aqueous solution "A4" was prepared with 9.2 weight percent
tetramethylammonium hydroxide (TMAH), 0.06 weight percent of the
non-ionic surfactant Surfynol-465 (a product of Air Products and
Chemicals, Inc.), 0.9 weight percent glacial acetic acid, 3.0
weight percent glycerol and 0.9 weight percent salicylic acid
(remainder of this solution being made up with de-ionized water)
and has a pH of about 12.5.
Aqueous solution "A5" was prepared with 2.4 weight percent
tetramethylammonium hydroxide (TMAH), 0.1 weight percent
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), 0.9
weight percent glacial acetic acid, 3.0 weight percent glycerol and
0.9 weight percent salicylic acid (remainder of this solution being
made up with de-ionized water) and has a pH of about 12.5.
Aqueous solution "A6" was prepared with 4.2 weight percent
tetramethylammonium hydroxide (TMAH), 0.1 weight percent
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), 0.06
weight percent of the non-ionic surfactant Surfynol-465 (a product
of Air Products and Chemicals, Inc.), 2.2 weight percent glacial
acetic acid, 3.0 weight percent glycerol and 0.9 weight percent
salicylic acid (remainder of this solution being made up with
de-ionized water) and has a pH of about 12.5.
Aqueous solution "A7" was prepared with 3.1 weight percent
tetramethylammonium hydroxide (TMAH), 1.1 weight percent
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), 0.06
weight percent of the non-ionic surfactant Surfynol-465 (a product
of Air Products and Chemicals, Inc.), 0.9 weight percent glacial
acetic acid, 3.0 weight percent glycerol and 0.9 weight percent
salicylic acid (remainder of this solution being made up with
de-ionized water) and has a pH of about 12.5.
Aqueous solution "A8" was prepared with 2.4 weight percent
tetramethylammonium hydroxide (TMAH), 0.1 weight percent
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), 0.07
weight percent of the non-ionic surfactant Surfynol-465 (a product
of Air Products and Chemicals, Inc.), 1.0 weight percent glacial
acetic acid and 1.0 weight percent salicylic acid (remainder of
this solution being made up with de-ionized water).
Aqueous solution "A9" was prepared with 2.3 weight percent
tetramethylammonium hydroxide (TMAH), 0.1 weight percent
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), 0.06
weight percent of the non-ionic surfactant Surfynol-465 (a product
of Air Products and Chemicals, Inc.), 0.9 weight percent glacial
acetic acid, 6.0 weight percent glycerol and 0.9 weight percent
salicylic acid (remainder of this solution being made up with
de-ionized water).
Aqueous solution "A10" was prepared with 2.1 weight percent
tetramethylammonium hydroxide (TMAH), 0.1 weight percent
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), 0.07
weight percent of the non-ionic surfactant Surfynol-465 (a product
of Air Products and Chemicals, Inc.), 0.9 weight percent glacial
acetic acid, 3.0 weight percent glycerol and 0.9 weight percent
acetone oxime (remainder of this solution being made up with
de-ionized water) and has a pH of about 12.3.
Aqueous solution "A11" was prepared with 2.3 weight percent
tetramethylammonium hydroxide (TMAH), 0.1 weight percent
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), 0.07
weight percent of the non-ionic surfactant Surfynol-465 (a product
of Air Products and Chemicals, Inc.), 3.0 weight percent glycerol
and 0.8 weight percent phosphoric acid (remainder of this solution
being made up with de-ionized water) and has a pH of about
12.2.
Wafer #1 samples with 0.35 micron wide via features had been
previously prepared using a via-first dual-damascene process with
the following layers present: Si wafer base, copper metal, silicon
nitride, fluorinated silica glass (FSG) dielectric, silicon nitride
etch-stop, FSG and anti-reflective coating (ARC) layers.
Lithographic patterning was done using a deep ultraviolet (DUV)
photoresist material. Reactive ion etching for pattern transfer was
followed by oxygen plasma ashing to remove organic photoresist
residues, but leaving mainly inorganic residues behind. A wafer
sample was placed in each of these solutions at 24-55.degree. C.
for 20 minutes, removed, rinsed with de-ionized water and dried
with pressurized nitrogen gas. After drying, the sample was
inspected on a Field Emission Scanning Electron Microscope (FE-SEM)
to determine the extent of cleaning and/or corrosion of the copper
metal features. The results are shown in Table 1.
TABLE 1 FE-SEM Evaluation Results pKa of Bath Post-Ash Copper Bath
Stabilizing Residue Metal Stabilizing Agent Used Temp. Removed
Corrosion Solution Description Agent Used (at 25.degree. C.)
(.degree. C.) (%) (% Metal Loss) A1 No silicate content. Salicylic
pKa.sub.2 = 12.4 24 88 1 Acid (very slight) 35 100 3 (very slight)
45 100 3 (very slight) 55 100 4 (very slight) A2 A1 with 2.4x
amount of Salicylic pKa.sub.2 = 12.4 45 100 7 bath stabilizing
agent Acid (slight) A3 A1 with acetic acid Salicylic pKa.sub.2 =
12.4 45 100 5 removed Acid (slight) A4 A1 with chelating agent
Salicylic pKa.sub.2 = 12.4 45 100 4 removed Acid (very slight) A5
A1 with surfactant Salicylic pKa.sub.2 = 12.4 45 100 7 removed Acid
(slight) A6 A1 with 2.4x amount of Salicylic pKa.sub.2 = 12.4 45
100 5 acetic acid Acid (slight) A7 A1 with 10x amount of Salicylic
pKa.sub.2 = 12.4 45 100 7 chelating agent Acid (slight) A8 A1 with
co-solvent Salicylic pKa.sub.2 = 12.4 24 98 1 removed Acid (very
slight) 35 100 3 (very slight) 45 100 5 (slight) A9 A1 with 2x
amount of Salicylic pKa.sub.2 = 12.4 45 100 3 co-solvent added Acid
(very slight) A10 A1 with acetone oxime Acetone pKa = 12.2 45 100 6
bath stabilizer Oxime (slight) substituted for salicylic acid A11
A1 with phosphoric acid Phosphoric pKa.sub.3 = 12.3 45 99 1 bath
stabilizer Acid (very substituted for salicylic slight) acid
Referring to Table 1, the data shows the ability of stabilized,
aqueous, alkaline solutions to successfully remove post-etch/ash
residues from a semiconductor wafer over a temperature range of
about 24-55.degree. C. This table also shows the ability to
substitute different bath stabilizing agents and still maintain the
cleaning efficiency of the solution.
Example 2
Aqueous solution "B1" was prepared with 2.5 weight percent
tetramethylammonium hydroxide (TMAH), 0.1 weight percent
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), 0.07
weight percent of the non-ionic surfactant Surfynol-465 (a product
of Air Products and Chemicals, Inc.), 3.0 weight percent glycerol,
0.14 weight percent (calculated as % SiO.sub.2) tetramethylammonium
silicate (TMAS), 0.95 weight percent glacial acetic acid and 0.8
weight percent 5-sulfosalicylic acid (remainder of this solution
being made up with de-ionized water) and has a pH of about
12.1.
Aqueous solution "B2" was prepared with 1.1 weight percent
tetramethylammonium hydroxide (TMAH), 0.1 weight percent
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), 0.08
weight percent of the non-ionic surfactant Surfynol-465 (a product
of Air Products and Chemicals, Inc.), 3.0 weight percent glycerol,
0.14 weight percent (calculated as % SiO.sub.2) tetramethylammonium
silicate (TMAS) and 0.8 weight percent 5-sulfosalicylic acid
(remainder of this solution being made up with de-ionized water)
and has a pH of about 12.1.
Aqueous solution "B3" was prepared with 3.2 weight percent
tetramethylammonium hydroxide (TMAH), 0.1 weight percent
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), 0.07
weight percent of the non-ionic surfactant Surfynol-465 (a product
of Air Products and Chemicals, Inc.), 3.0 weight percent glycerol,
0.14 weight percent (calculated as % SiO.sub.2) tetramethylammonium
silicate (TMAS) and 2.9 weight percent 5-sulfosalicylic acid
(remainder of this solution being made up with de-ionized water)
and has a pH of about 12.1.
Aqueous solution "B4" was prepared with 1.9 weight percent
tetramethylammonium hydroxide (TMAH), 0.08 weight percent
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), 0.06
weight percent of the non-ionic surfactant Surfynol-465 (a product
of Air Products and Chemicals, Inc.), 24 weight percent glycerol,
0.11 weight percent (calculated as % SiO.sub.2) tetramethylammonium
silicate (TMAS), 0.7 weight percent glacial acetic acid and 0.6
weight percent 5-sulfosalicylic acid (remainder of this solution
being made up with de-ionized water).
Aqueous solution "B5" was prepared with 1.9 weight percent
tetramethylammonium hydroxide (TMAH), 0.08 weight percent
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), 0.06
weight percent of the non-ionic surfactant Surfynol-465 (a product
of Air Products and Chemicals, Inc.), 27 weight percent glycerol,
0.10 weight percent (calculated as % SiO.sub.2) tetramethylammonium
silicate (TMAS), 0.7 weight percent glacial acetic acid and 0.6
weight percent 5-sulfosalicylic acid (remainder of this solution
being made up with de-ionized water).
Aqueous solution "C" was prepared with 2.5 weight percent
tetramethylammonium hydroxide (TMAH), 0.1 weight percent
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), 0.06
weight percent of the non-ionic surfactant Surfynol-465 (a product
of Air Products and Chemicals, Inc.), 3.0 weight percent glycerol,
1.0 weight percent (calculated as % SiO.sub.2) tetramethylammonium
silicate (TMAS), 0.9 weight percent glacial acetic acid and 0.9
weight percent salicylic acid (remainder of this solution being
made up with de-ionized water) and has a pH of about 12.5.
Aqueous solution "D" was prepared with 3.3 weight percent
tetramethylammonium hydroxide (TMAH), 0.1 weight percent
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), 0.07
weight percent of the non-ionic surfactant Surfynol-465 (a product
of Air Products and Chemicals, Inc.), 3.0 weight percent glycerol,
0.28 weight percent (calculated as % SiO.sub.2) tetramethylammonium
silicate (TMAS) and 3.0 weight percent 5-sulfosalicylic acid
(remainder of this solution being made up with de-ionized water)
and has a pH of about 12.1.
Aqueous solution "E1" was prepared with 3.2 weight percent
tetramethylammonium hydroxide (TMAH), 0.1 weight percent
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), 0.07
weight percent of the non-ionic surfactant Surfynol-465 (a product
of Air Products and Chemicals, Inc.), 3.0 weight percent glycerol,
0.22 weight percent (calculated as % SiO.sub.2) tetramethylammonium
silicate (TMAS) and 2.9 weight percent 5-sulfosalicylic acid
(remainder of this solution being made up with de-ionized water)
and has a pH of about 12.1.
Aqueous solution "E2" was prepared with 3.0 weight percent
tetramethylammonium hydroxide (TMAH), 0.1 weight percent
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), 0.06
weight percent of the non-ionic surfactant Surfynol-465 (a product
of Air Products and Chemicals, Inc.), 9.0 weight percent glycerol,
0.21 weight percent (calculated as % SiO.sub.2) tetramethylammonium
silicate (TMAS) and 2.8 weight percent 5-sulfosalicylic acid
(remainder of this solution being made up with de-ionized
water).
Aqueous solution "E3" was prepared with 2.7 weight percent
tetramethylammonium hydroxide (TMAH), 0.09 weight percent
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), 0.06
weight percent of the non-ionic surfactant Surfynol-465 (a product
of Air Products and Chemicals, Inc.), 18 weight percent glycerol,
0.12 weight percent (calculated as % SiO.sub.2) tetramethylammonium
silicate (TMAS) and 2.5 weight percent 5-sulfosalicylic acid
(remainder of this solution being made up with de-ionized
water).
Aqueous solution "F1" was prepared with 4.0 weight percent
tetramethylammonium hydroxide (TMAH), 0.1 weight percent
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), 0.06
weight percent of the non-ionic surfactant Surfynol-465 (a product
of Air Products and Chemicals, Inc.), 3.0 weight percent glycerol,
0.28 weight percent (calculated as % SiO.sub.2) tetramethylammonium
silicate (TMAS) and 1.6 weight percent phosphoric acid (remainder
of this solution being made up with de-ionized water) and has a pH
of about 12.1.
Aqueous solution "F2" was prepared with 2.5 weight percent
tetramethylammonium hydroxide (TMAH), 0.1 weight percent
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), 0.06
weight percent of the non-ionic surfactant Surfynol-465 (a product
of Air Products and Chemicals, Inc.), 3.0 weight percent glycerol,
0.26 weight percent (calculated as % SiO.sub.2) tetramethylammonium
silicate (TMAS) and 0.97 weight percent phosphoric acid (remainder
of this solution being made up with de-ionized water) and has a pH
of about 12.1.
Aqueous solution "F3" was prepared with 1.5 weight percent
tetramethylammonium hydroxide (TMAH), 0.1 weight percent
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), 0.06
weight percent of the non-ionic surfactant Surfynol-465 (a product
of Air Products and Chemicals, Inc.), 3.0 weight percent glycerol,
0.22 weight percent (calculated as % SiO.sub.2) tetramethylammonium
silicate (TMAS) and 0.53 weight percent phosphoric acid (remainder
of this solution being made up with de-ionized water) and has a pH
of about 12.1.
Aqueous solution "G" was prepared with 2.0 weight percent
tetramethylammonium hydroxide (TMAH), 0.1 weight percent
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), 0.15
weight percent (calculated as % SiO.sub.2) tetramethylammonium
silicate (TMAS) and 1.6 weight percent hydrogen peroxide (remainder
of this solution being made up with de-ionized water) and has a pH
of about 11.5.
Wafer #1 samples with 0.35 micron wide via features had been
previously prepared using a via-first dual-damascene process with
the following layers present: Si wafer base, copper metal, silicon
nitride, fluorinated silica glass (FSG) dielectric, silicon nitride
etch-stop, FSG and anti-reflective coating (ARC) layers.
Lithographic patterning was done using a deep ultraviolet (DUV)
photoresist material. Reactive ion etching for pattern transfer was
followed by oxygen plasma ashing to remove organic photoresist
residues, but leaving mainly inorganic residues behind. Wafer #2
samples with one micron wide features and Aluminum-Copper raised
lines capped with titanium-nitride, were previously prepared as
follows: (a) a coating of spin-on-glass was applied to a silicon
wafer and cured (b) a titanium adhesion layer was applied (c) a
titanium nitride layer was deposited (d) metallization with an
aluminum-1% copper alloy (e) a titanium nitride capping layer was
deposited (f) lithographic patterning using a photoresist material
(g) pattern transfer using reactive ion etching and (h) oxygen
plasma ashing to remove organic photoresist residues, but leaving
mainly inorganic residues behind. Wafer samples #3 through #6 have
0.35 micron wide features and Aluminum-Copper raised lines capped
with titanium-nitride, were previously prepared as follows: (a) a
coating of spin-on-glass was applied to a silicon wafer and cured
(b) a titanium adhesion layer was applied (c) a titanium nitride
layer was deposited (d) metallization with an aluminum-1% copper
alloy (e) a titanium nitride capping layer was deposited (f)
lithographic patterning using a photoresist material (g) pattern
transfer using reactive ion etching and (h) oxygen plasma ashing to
remove organic photoresist residues, but leaving mainly inorganic
residues behind. Wafer sample #7 with 0.3-0.5 micron wide by 0.5
micron deep holes (vias) through dielectric and titanium nitride
layers exposing aluminum-copper alloy metal at the base had been
previously processed as follows (a) metallization with
aluminum-copper followed by titanium nitride (b) coated with
silicon oxide dielectric using chemical vapor deposition (c)
lithographic patterning of vias using a photoresist material (d)
pattern transfer to the dielectric layer using a reactive ion
etching (e) oxygen plasma ashing to remove most of the residual
photoresist, but leaving mainly inorganic residues behind, were
used to evaluate the performance of the solutions. A wafer sample
was placed in each of these solutions at 22-65.degree. C. for 10-60
minutes, removed, rinsed with de-ionized water and dried with
pressurized nitrogen gas. After drying, the sample was inspected on
a Field Emission Scanning Electron Microscope (FE-SEM) to determine
the extent of cleaning and/or corrosion of the metal features. The
results are shown in Table 2.
TABLE 2 FE-SEM Evaluation Results pKa of Bath Wafer Sample Time
Post-Ash Copper Bath Stabilizing Number Tested (min.)/ Residue
Metal Stabilizing Agent Used (1 = Cu-based, 2-7 = Al/Cu Temp.
Removed Corrosion Solution Description Agent Used (at 25.degree.
C.) alloy based) (.degree. C.) (%) (% Metal Loss) B1 Contains 5-
pKa.sub.2 = 12.0 2 10/22 100 0 silicate. sulfosalicylic 1 20/35 95
0 Acid 1 20/45 100 4 (very slight) 1 20/55 100 6 (slight) 3 20/25
100 15 (light) B2 B1 with 5- pKa.sub.2 = 12.0 2 10/22 100 1 acetic
acid sulfosalicylic (very removed Acid slight) 1 20/35 98 1 (very
slight) 1 20/45 100 5 (slight) 1 20/55 100 7 (slight) B3 B1 with
3.6x 5- pKa.sub.2 = 12.0 2 10/22 100 1 amount of sulfosalicylic
(very bath Acid slight) stabilizing 1 20/24 50 0 agent 1 20/35 70 0
1 20/45 100 5 (slight) 1 20/55 100 7 (slight) 1 20/65 100 10
(light) B4 B1 with 6x 5- pKa.sub.2 = 12.0 3 60/35 100 5 co-solvent
sulfosalicylic (slight) added Acid B5 B1 with 7x 5- pKa.sub.2 =
12.0 3 60/35 100 3 co-solvent sulfosalicylic (very added Acid
slight) B6 B1 with 8x 5- pKa.sub.2 = 12.0 3 60/35 99 0 co-solvent
sulfosalicylic added Acid B7 B1 with 9x 5- pKa.sub.2 = 12.0 3 60/35
95 0 co-solvent sulfosalicylic added Acid C Contains Salicylic
pKa.sub.2 = 12.4 2 10/22 100 0 silicate. acid 1 20/35 90 2 (very
slight) 1 20/45 99 5 (slight) 1 20/55 100 5 (slight) 1 20/65 100 8
(slight) D Contains 5- pKa.sub.2 = 12.0 5 10/25 100 0 silicate.
sulfosalicylic 5 40/25 100 8 Acid (slight) E1 Contains 5- pKa.sub.2
= 12.0 5 10/25 100 0 silicate. sulfosalicylic 5 40/25 100 9 Acid
(slight) 6 20/30 100 2 (very slight) E2 E1 with 3x 5- pKa.sub.2 =
12.0 5 40/25 100 1 co-solvent sulfosalicylic (very added Acid
slight) E3 E1 with 50% 5- pKa.sub.2 = 12.0 5 40/25 100 9 silicate
sulfosalicylic (slight) content and Acid with 6x co- solvent added
F1 Contains Phosphoric pKa.sub.3 = 12.3 5 40/25 100 9 silicate.
Acid (slight) 6 15/30 100 1 (very slight) 6 20/30 100 3 (very
slight) 6 10/35 100 3 (very slight) F2 F1 with 40% Phosphoric
pKa.sub.3 = 12.3 5 40/25 100 9 less bath Acid (slight) stabilizing
6 15/30 100 3 agent added (very slight) 6 20/30 100 5 (slight) 6
10/35 100 5 (slight) F3 F1 with 66% Phosphoric pKa.sub.3 = 12.3 5
40/25 100 9 less bath Acid (slight) stabilizing 6 15/30 100 2 agent
added (very slight) 6 20/30 100 4 (very slight) 6 10/35 100 5
(slight) G Contains Hydrogen pKa = 11.6 7 10/45 100 5 silicate.
Peroxide (slight)
Referring to Table 2, the data shows the ability of stabilized,
aqueous, alkaline solutions containing silicate to successfully
remove post-etch/ash residues from a semiconductor wafers over a
temperature range of about 25-65.degree. C. This table also shows
the ability to substitute different bath stabilizing agents with
different pKa values and still maintain the cleaning efficiency of
the solution.
Example 3
Aqueous solution "H" was prepared (without any bath stabilizing
agent added) with 0.2 weight percent tetramethylammonium hydroxide
(TMAH), 0.1 weight percent
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), 0.07
weight percent of the non-ionic surfactant Surfynol-465 (a product
of Air Products and Chemicals, Inc.), 3.0 weight percent glycerol
and 0.14 weight percent (calculated as % SiO.sub.2)
tetramethylammonium silicate (TMAS) (remainder of this solution
being made up with de-ionized water) and has a pH of about
12.0.
Comparative 4 L uncovered baths were set up in a chemical fume hood
with an air-flow rate of about 100 feet per minute (FPM) over the
baths. The temperature of the baths was maintained by use of
programmable digital hot plates with a bath temperature monitoring
probe. Wafer samples were processed during the aging of the
solutions so as to determine its performance bath-life. A
description of the solutions used for the comparisons is discussed
above in Examples 1 and 2. A wafer sample was placed in each of
these solutions at 30-55.degree. C. for 10-20 minutes, removed,
rinsed with de-ionized water and dried with pressurized nitrogen
gas. After drying, the sample was inspected on a Field Emission
Scanning Electron Microscope (FE-SEM) to determine the extent of
cleaning and/or corrosion of the metal features. The bath aging
results are shown in Table 3a.
TABLE 3 FE-SEM Evaluation Results for Aged Solutions Amount of Bath
Bath Wafer Sample Bath Stabilizing Aging Wafer Process Bath Aging
time with Stabilizing Agent Added Temp. Sample Conditions
Successful Cleaning of Solution Agent Added (Weight %) (.degree.
C.) Number (min./.degree. C.) Samples (Hours) H none 0 35 6 20/35
12 E1 5-Sulfosalicylic 2.9 30 6 20/30 28 Acid F1 Phosphoric 1.6 35
6 10/35 29 Acid F2 Phosphoric 0.97 30 6 20/30 20 Acid F3 Phosphoric
0.53 30 6 20/30 24 Acid A1 Salicylic Acid 0.93 45 1 20/45 24 B1
5-Sulfosalicylic 0.82 45 1 20/45 24 Acid C Salicylic Acid 0.94 55 1
20/55 24 G Hydrogen 1.6 45 7 10/45 24 Peroxide
Referring to Table 3, the data clearly shows the ability of
stabilized, aqueous, alkaline solutions to successfully remove
post-etch/ash residues from semiconductor wafers for a longer
period of time in an aged open bath. This table clearly shows that
the lack of a stabilizing agent results in a bath-life that is
unacceptably short. This table also shows the ability to substitute
different bath stabilizing agents and still maintain the cleaning
efficiency of the solution.
Example 4
Aqueous, unstabilized stock solution "K1" was prepared with 0.18
weight percent tetramethylammonium hydroxide (TMAH), 0.1 weight
percent trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA),
0.07 weight percent of the non-ionic surfactant Surfynol-465 (a
product of Air Products and Chemicals, Inc.), 0.14 weight percent
(calculated as % SiO.sub.2) tetramethylammonium silicate (TMAS) and
6.0weight percent glycerol (remainder of this solution being made
up with de-ionized water) and has a pH of about 11.78 at
25.0.degree. C.
Aqueous, stabilized solution "K40" was prepared with 100.00 g of
stock solution "K1", 10.21 g of 25.2 wt. % tetramethylammonium
carbonate and 0.24 g of 24.85 wt. % TMAH (remainder of this
solution being made up with de-ionized water) and has a pH of about
11.76 at 25.0.degree. C. Aqueous, stabilized solution "K41" was
prepared with 2.6 weight percent tetramethylammonium hydroxide
(TMAH), 5.0 weight percent of the bath stabilizing agent
2-hydroxypyridine, 0.05 weight percent of the non-ionic surfactant
Surfynol-465 (a product of Air Products and Chemicals, Inc.), 0.12
weight percent (calculated as % SiO.sub.2) tetramethylammonium
silicate (TMAS), 5.2 weight percent glycerol and 0.09 weight
percent of the metal chelating agent
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA) with the
remainder of this solution being made up with de-ionized water and
has a pH of about 11.90 at 25.0.degree. C. Aqueous, stabilized
solution "K42" was prepared with 2.5 weight percent
tetramethylammonium hydroxide (TMAH), 5.0 weight percent of the
bath stabilizing agent 2-hydroxypyridine, 0.05 weight percent of
the non-ionic surfactant Surfynol-465 (a product of Air Products
and Chemicals, Inc.), 0.12 weight percent (calculated as %
SiO.sub.2) tetramethylammonium silicate (TMAS), 5.2 weight percent
glycerol with the remainder of this solution being made up with
de-ionized water and has a pH of about 11.89 at 25.0.degree. C.
Stabilized solutions were prepared by adding a bath stabilizing
agent to 200.1 g of the above stock solution and adjusting the pH
back to about 11.8 with 24.85% TMAH, if necessary. Table 4a
summarizes the results of the small beaker aging test for potential
bath stabilizing agents with a pKa in the 10-13 range. If a bath
stabilizing agent has more than one pKa associated with it, then
only the pKa in the 10-13 range is shown in Table 4a. The pH drop
comparison was done by measuring the pH of the solution aged in a
sealed poly bottle and compare it to the same solution aged in an
uncovered 100 ml small beaker for 20 hours at room temperature.
Table 4b summarizes the results of the small beaker aging test for
potential bath stabilizing agents with a pKa in the 10-13 range. If
a bath stabilizing agent has more than one pKa associated with it,
then only the pKa in the 10-13 range is shown in Table 4b. The pH
drop comparison was done by measuring the pH of the unaged solution
then aging the solution for 16 hours in an open 150 ml glass beaker
placed in a chemical fume hood at room temperature. After 16 hours
the pH of the aged solution is taken and the pH drop
determined.
Table 4c summarizes the results of the small beaker aging test for
potential bath stabilizing agents with a pKa in the 10-13 range
with and without the optional metal chelating agent added to the
solution. If a bath stabilizing agent has more than one pKa
associated with it, then only the pKa in the 10-13 range is shown
in Table 4c. The pH drop comparison was done by measuring the pH of
the solution aged in a sealed poly bottle and compare it to the
same solution aged in an uncovered 100 ml small beaker for 20 hours
at room temperature.
All potential bath stabilizing agents were obtained from either
Aldrich or the J. T. Baker Division of Mallinckrodt Baker, Inc. The
2-Hydroxypyridine and 4-hydroxypyridine used was purchased from
Aldrich and used without further purification.
TABLE 4a 20 Hour Uncovered Small Beaker Aging Test pKa of Amount of
pH Drop Conc. of Bath Bath Bath Amount 24.85% Freshly After PH Drop
Bath Stabilizing Stabilizing Stabilizing TMAH Added Made Aging in
After Aging Stabilizing Agent Agent Used Agent Added to Adjust pH
Solution a Sealed 20 Hours Solution Agent Used (wt. %) (at
25.degree. C.) (grams) (grams) pH Poly Bottle* in Open Beaker K1
None 0 11.78 no Ave. = 0.78 K2 Acetone 2.8 12.2 6.01 6.18 11.80
slight 0.50 Oxime K3 Acetone 5.5 12.2 12.06 5.14 11.78 slight 0.39
Oxime K4 Salicyl- 2.5 12.11 6.00 32.77 11.78 no 0.28 aldoxime K5
5-Sulfo- 2.7 12.00 6.07 20.70 11.80 no 0.17 salicylic Acid K6
Resorcinol 2.5 12.32 6.02 32.29 11.63 no 0.07 K7 Resorcinol 8.5
12.32 35.10 177.75 11.83 no 0.05 (incr.)** K8 2-Methyl- 2.6 11.64
6.02 22.41 11.78 slight 0.13 resorcinol K9 2-Methyl- 5.5 11.64
resorcinol (not fully dissolved) K10 Orcinol 2.7 .about.11-12 6.40
30.66 11.81 slight 0.11 (estimated) K11 Proline 2.9 10.96 6.40
17.62 11.87 no 0.77 K12 2-Methyl- 3.1 11.2 6.40 0 12.24 no 0.56
1,5-pentane- diamine K13 Piperidine 3.1 11.12 6.40 0 12.41 no 0.74
K14 Pyrrolidine 3.1 11.31 6.40 0 12.49 no 0.50 K15 4-Methyl- 3.1
11.23 6.40 0 12.36 no 0.97 piperidine K16 Saccharin 2.7 11.68 6.00
12.25 11.80 no 0.64 K17 4-hydroxy- 0.10 11.09 0.21 0.99 11.94 no
0.66 pyridine K18 4-hydroxy- 2.7 11.09 6.02 18.96 11.80 no 0.14
pyridine K19 4-hydroxy- 6.0 11.09 15.90 49.64 11.82 no 0.06
pyridine K20 4-hydroxy- 9.0 11.09 28.30 87.30 11.84 no 0.03
pyridine K21 4-hydroxy- 12.5 11.09 50.00 149.09 11.82 no 0 pyridine
K22 2-Hydroxy- 0.10 11.62 0.21 0.66 11.89 no 0.61 pyridine K23
2-Hydroxy- 0.97 11.62 2.01 4.11 11.82 no 0.19 pyridine K24
2-Hydroxy- 1.4 11.62 3.01 5.78 11.82 no 0.15 pyridine K25
2-Hydroxy- 2.8 11.62 6.02 11.04 11.79 no 0.09 pyridine K26
2-Hydroxy- 4.0 11.62 9.03 16.45 11.82 no 0.05 pyridine K27
2-Hydroxy- 5.0 11.62 11.70 21.10 11.82 no 0.04 pyridine K28
2-Hydroxy- 6.0 11.62 14.50 26.11 11.83 no 0.03 pyridine K29
2-Hydroxy- 9.0 11.62 23.80 39.59 11.82 no 0.02 pyridine K30
2-Hydroxy- 12.2 11.62 35.60 56.98 11.83 no 0 pyridine K31
2-Hydroxy- 15.0 11.62 50.00 83.32 11.90 no 0 pyridine K32 Benzimid-
<3 12.3 11.8 no 0.5 azole (saturated) K33 Cyanuric .about.1.5
11.10 Acid (insoluble.sup.#) K34 Dibutyl- .about.3 11.25 amine
(insoluble.sup.#) K35 Dimethyl- .about.3 .about.12 glyoxime
(insoluble.sup.#) (estimated) K36 Acetamidine .about.3 12.4
(insoluble.sup.#) K37 2-Methyl- .about.3 10.95 piperidine
(insoluble.sup.#) K38 3-Methyl- .about.3 11.07 piperidine
(insoluble.sup.#) K39 4-Hydroxy- .about.3 .about.11 piperidine
(insoluble.sup.#) (estimated) *Any pH drop noted in the sealed poly
bottle is likely due to oxidation of the buffer and was monitored
over the course of several days. A "slight" pH drop rating
corresponds to <0.10 pH units, which may be related to pH
standardization errors. **pH increased by 0.05, which would be
expected as water evaporated off (typically, about 10 wt. % water
was lost due to evaporation during uncovered beaker aging). .sup.#
Insoluble despite addition of 25% aqueous TMAH to achieve pH
.about.12.
TABLE 4b 16 Hour Uncovered Small Beaker Aging Test Conc. Of Bath
pKa of Bath Freshly pH After pH Drop After Bath Stabilizing
Stabilizing Agent Stabilizing Agent Used Made Aging 16 Aging 16
Hours in Solution Agent Used (as wt. % Carbonate) (at 25.degree.
C.) Solution pH Hours Open Beaker K1 None 0 11.77 11.19 0.58 K40
TMA Carbonate 0.67 10.33 11.76 11.34 0.42
Referring to Table 4a and Table 4b above, it is clear that not all
bath stabilizing agents with a pKa in the 10-13 range would be
effective in stabilizing these aqueous solutions against changes in
pH. It is apparent that the best bath stabilizing agents are those
that are NOT selected from the following: (a) reducing agents that
could be easily oxidized by exposure to the air, (b) have a low
boiling point such that the stabilizing agent would evaporate
during exposure to the air, (c) have a solubility of less than 0.5
wt. % in aqueous alkaline solution. It is also apparent that
choosing a bath stabilizing agent with a pKa as low as 10.3 is
still useful for buffering a solution at a pH of about 11.8. Table
4a also clearly demonstrates that as the concentration of the bath
stabilizing agent is increased the pH stability of the formulations
are increased.
TABLE 4c 20 Hour Uncovered Small Beaker Aging Test Bath Conc. of
Bath pKa of Bath Metal Freshly Made pH After pH Drop After
Stabilizing Stabilizing Agent Stabilizing Agent Used Chelating
Solution Aging 20 Aging 20 Hours Solution Agent Used (wt. %) (at
25.degree. C.) Agent Added? pH Hours in Open Beaker K1 None 0 YES
11.79 10.97 0.82 K41 2-Hydroxy- 5.0 11.62 YES 11.90 11.85 0.05
pyridine K42 2-Hydroxy- 5.0 11.62 NO 11.89 11.84 0.05 pyridine
Referring to Table 4c, it is apparent that the presence of a metal
chelating agent is optional and has no effect on the pH stability
of the solution.
Example 5
Aqueous, unstabilized stock solution "L1" was prepared with 0.79
weight percent tetramethylammonium hydroxide (TMAH), 0.11 weight
percent trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA),
0.07 weight percent of the non-ionic surfactant Surfynol-465 (a
product of Air Products and Chemicals, Inc.), 0.14 weight percent
(calculated as % SiO.sub.2) tetramethylammonium silicate (TMAS) and
18.5weight percent hydroxylamine (remainder of this solution being
made up with de-ionized water) and has a pH of about 11.95 at
25.0.degree. C.
Stabilized solutions were prepared by adding a bath stabilizing
agent to 200.0 g of the above stock solution and adjusting the pH
back to about 11.95 with 24.85% TMAH. Table 5 summarizes the
results of the small beaker aging test for bath stabilizing agents
with a pKa in the 10-13 range. If a bath stabilizing agent has more
than one pKa associated with it, then only the pKa in the 10-13
range is shown in Table 5. The pH drop comparison was done by
measuring the pH of the solution aged in a sealed poly bottle to
the same solution aged in an uncovered small beaker for 20 hours at
room temperature.
TABLE 5 20 Hour Uncovered Small Beaker Aging Test pKa of Amount of
pH Drop Conc. Of Bath Bath Bath Amount 24.85% Freshly After pH Drop
Bath Stabilizing Stabilizing Stabilizing TMAH Added Made Aging in
After Aging Stabilizing Agent Agent Used Agent Added to Adjust pH
Solution a Sealed 20 Hours Solution Agent Used (wt. %) (at
25.degree. C.) (grams) (grams) pH Poly Bottle* in Open Beaker L1
None 0 11.95 no Ave. = 1.84 L2 2-Hydroxy- 5.0 11.62 11.70 23.05
11.96 no 0.28 pyridine L3 2-Hydroxy- 11.2 11.62 32.73 58.39 11.95
no 0.11 pyridine L4 2-Hydroxy- 16.6 11.62 58.03 90.99 11.94 no 0.08
pyridine L5 2-Hydroxy- 22.1 11.62 95.00 134.29 11.94 no 0.05
pyridine *Any pH drop noted in the sealed poly bottle is likely due
to oxidation of the buffer and was monitored over the course of
several days. A "slight" pH drop rating corresponds to <0.10 pH
units, which may be related to pH standardization errors.
Referring to Table 5 above, the unbuffered aqueous,
hydroxylamine-containing formulation had a significant change in pH
after aging. The addition of a bath stabilizing agent to the
aqueous, hydroxylamine-containing solution dramatically improved
the pH stability of the formulation. The table also clearly
demonstrates that as the concentration of the bath stabilizing
agent is increased the pH stability of the formulations are
increased. Also, by extrapolation of the data in Table 5, a minimum
concentration of about 31-35 wt. % 2-hydroxypyridine would be
required to eliminate any pH drop under these test conditions.
However, the actual amount required may be greater if the
solution's pH stabilization behaves in an exponential rather than
linear manner and may require as much as 50 wt. % 2-hydroxypyridine
to eliminate any pH drop under these test conditions.
Example 6
Aqueous, stabilized solution "M1" was prepared with 3.0 weight
percent of the bath stabilizing agent piperidine, 0.06 weight
percent of the non-ionic surfactant Surfynol-465 (a product of Air
Products and Chemicals, Inc.), 0.12 weight percent (calculated as %
SiO.sub.2) tetramethylammonium silicate (TMAS), 5.0 weight percent
glycerol and the pH adjusted to about 11.77 at 25.0.degree. C. by
adding 0.95 weight percent
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA) with the
remainder of this solution being made up with de-ionized water.
Aqueous, stabilized solution "M2" was prepared with 3.0 weight
percent of the bath stabilizing agent pyrrolidine, 0.06 weight
percent of the non-ionic surfactant Surfynol-465 (a product of Air
Products and Chemicals, Inc.), 0.12 weight percent (calculated as %
SiO.sub.2) tetramethylammonium silicate (TMAS), 5.0 weight percent
glycerol and the pH adjusted to about 11.79 at 25.0.degree. C. by
adding 1.1 weight percent (ethylenedinitrilo)tetraacetic acid
(EDTA), with the remainder of this solution being made up with
de-ionized water.
Aqueous, stabilized solution "M3" was prepared with 3.0 weight
percent of the bath stabilizing agent 2-methyl-1,5-pentanediamine,
0.06 weight percent of the non-ionic surfactant Surfynol-465 (a
product of Air Products and Chemicals, Inc.), 0.12 weight percent
(calculated as % SiO.sub.2) tetramethylammonium silicate (TMAS),
5.1 weight percent glycerol and the pH adjusted to about 11.81 at
25.0.degree. C. by adding 0.14 weight percent
(ethylenedinitrilo)tetraacetic acid (EDTA), with the remainder of
this solution being made up with de-ionized water.
Aqueous, stabilized solution "M4" was prepared with 5.9 weight
percent of the bath stabilizing agent 2-methyl-1,5-pentanediamine,
0.06 weight percent of the non-ionic surfactant Surfynol-465 (a
product of Air Products and Chemicals, Inc.), 0.12 weight percent
(calculated as % SiO.sub.2) tetramethylammonium silicate (TMAS),
4.9 weight percent glycerol and the pH adjusted to about 11.79 at
25.0.degree. C. by adding 0.44 weight percent
(ethylenedinitrilo)tetraacetic acid (EDTA), with the remainder of
this solution being made up with de-ionized water.
Table 6 summarizes the results of the small beaker aging test for
bath stabilizing agents with a pKa in the 10-13 range. If a bath
stabilizing agent has more than one pKa associated with it, then
only the pKa in the 10-13 range is shown in Table 6. The pH drop
comparison was done by measuring the pH of the solution aged in a
sealed poly bottle to the same solution aged in an uncovered small
beaker for 20 hours at room temperature.
TABLE 6 20 Hour Uncovered Small Beaker Aging Test Conc. of Bath pKa
of Bath pH Drop After Aging Bath Stabilizing Stabilizing Agent
Stabilizing Agent Used Freshly Made 20 Hours in Open Solution Agent
Used (wt. %) (at 25.degree. C.) Solution pH Beaker K1 None 0 11.78
Ave. = 0.78 M1 Piperidine 3.0 11.12 11.77 0.66 M2 Pyrrolidine 3.0
11.31 11.79 0.46 M3 2-methyl-1,5- 3.0 11.2 11.81 0.41
pentanediamine M4 2-methyl-1,5- 5.9 11.2 11.79 0.29
pentanediamine
Referring to Table 6 above, there is a clear benefit to adding an
alkaline bath stabilizing agent to these aqueous formulations for
reducing the pH drop associated with their exposure to the air over
time. The table also clearly demonstrates that as the concentration
of the bath stabilizing agent is increased the pH stability of the
formulations are increased. The advantage in using an alkaline bath
stabilizing agent is that since TMAH has no measurable pKa (it is
fully dissociated in water) it does not stabilize the solution that
it is in. An alkaline bath stabilizing agent will achieve the
desired pH and also afford bath pH stability at the same time with
one less component added to the formulation. Another advantage of
using an alkaline bath stabilizing agent is that it may be combined
with one or more additional bath stabilizing agents to afford the
maximum bath pH stability for a formulation.
Example 7
Aqueous, stabilized solution "N1" was prepared with 3.0 weight
percent tetramethylammonium hydroxide (TMAH), 0.1 weight percent
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), 0.06
weight percent of the non-ionic surfactant Surfynol-465 (a product
of Air Products and Chemicals, Inc.), 0.21 weight percent
(calculated as % SiO.sub.2) tetramethylammonium silicate (TMAS),
9.0 weight percent glycerol and 2.8 weight percent of the bath
stabilizing agent 5-sulfosalicylic acid (remainder of this solution
being made up with de-ionized water) and has a pH of about 11.94 at
25.0.degree. C.
Aqueous, stabilized solution "N2" was prepared by adding
2-hydroxypyridine to stock solution "K1" and adjusting the pH back
to it's starting pH by adding additional 25 wt. % TMAH. Solution
"N2" contains: 1.4 weight percent tetramethylammonium hydroxide
(TMAH), 0.1 weight percent
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), 0.06
weight percent of the non-ionic surfactant Surfynol-465 (a product
of Air Products and Chemicals, Inc.), 0.13 weight percent
(calculated as % SiO.sub.2) tetramethylammonium silicate (TMAS),
5.6 weight percent glycerol and 2.8 weight percent of the bath
stabilizing agent 2-hydroxypyridine (remainder of this solution
being made up with de-ionized water) and has a pH of about 11.80 at
25.0.degree. C.
Aqueous, stabilized solution "N3" was prepared by adding
4-hydroxypyridine to stock solution "K1" and adjusting the pH back
to it's starting pH by adding additional 25 wt. % TMAH. Solution
"N3" contains: 2.3 weight percent tetramethylammonium hydroxide
(TMAH), 0.09 weight percent
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), 0.06
weight percent of the non-ionic surfactant Surfynol-465 (a product
of Air Products and Chemicals, Inc.), 0.12 weight percent
(calculated as % SiO.sub.2) tetramethylammonium silicate (TMAS),
5.4 weight percent glycerol and 2.7 weight percent of the bath
stabilizing agent 4-hydroxypyridine (remainder of this solution
being made up with de-ionized water) and has a pH of about 11.80 at
25.0.degree. C.
Aqueous, stabilized solution "N4" was prepared by adding resorcinol
to stock solution "K1" and adjusting the pH back to it's starting
pH by adding additional 25 wt. % TMAH. Solution "N4" contains: 3.7
weight percent tetramethylammonium hydroxide (TMAH), 0.09 weight
percent trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA),
0.06 weight percent of the non-ionic surfactant Surfynol-465 (a
product of Air Products and Chemicals, Inc.), 0.11 weight percent
(calculated as % SiO.sub.2) tetramethylammonium silicate (TMAS),
5.0 weight percent glycerol and 2.5 weight percent of the bath
stabilizing agent resorcinol (remainder of this solution being made
up with de-ionized water) and has a pH of about 11.78 at
25.0.degree. C.
Aqueous, stabilized solution "N5" was prepared by adding
2-hydroxypyridine to stock solution "K1" and adjusting the pH back
to it's starting pH by adding additional 25 wt. % TMAH. Solution
"N5" contains: 2.9 weight percent tetramethylammonium hydroxide
(TMAH), 0.09 weight percent
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), 0.06
weight percent of the non-ionic surfactant Surfynol-465 (a product
of Air Products and Chemicals, Inc.), 0.11 weight percent
(calculated as % SiO.sub.2) tetramethylammonium silicate (TMAS),
5.0 weight percent glycerol and 6.0 weight percent of the bath
stabilizing agent 2-hydroxypyridine (remainder of this solution
being made up with de-ionized water) and has a pH of about 11.83 at
25.0.degree. C.
Wafer sample #8 with 0.35 micron wide features and Aluminum-Copper
raised lines capped with titanium-nitride, were previously prepared
as follows: (a) a coating of spin-on-glass was applied to a silicon
wafer and cured (b) a titanium adhesion layer was applied (c) a
titanium nitride layer was deposited (d) metallization with an
aluminum-1% copper alloy (e) a titanium nitride capping layer was
deposited (f) lithographic patterning using a photoresist material
(g) pattern transfer using reactive ion etching and (h) oxygen
plasma ashing to remove organic photoresist residues, but leaving
mainly inorganic residues behind. The residues formed on the
aluminum sidewalls of this wafer were easily cleaned by the aqueous
formulations above in less than 5 minutes at 25.degree. C.
Therefore, this wafer proved useful for comparing aluminum metal
sidewall etch-rates after an extended treatment time.
A section from wafer sample #8 was treated in one of the solutions
above for 40 minutes (with the exception of solution N1, which was
10 minutes) at either 25, 30, 35 or 40.degree. C. Once the
treatment was completed it was removed, rinsed with de-ionized
water and dried with pressurized nitrogen gas. Then the samples
were cross-sectioned perpendicular to the direction of a parallel
line pattern, Pd--Au coated and then inspected in a Field Emission
Scanning Electron Microscope (FE-SEM). The FE-SEM inspection was
used to measure the amount of aluminum metal sidewall loss that had
occurred during the treatment and calculate an aluminum metal
sidewall etch-rate for each temperature. The results are shown in
Tables 7a and 7b below.
TABLE 7a Al-1% Cu Metal Sidewall Etch-Rate Comparison for Wafer #8
Determined by FE-SEM Amount of Al/Cu Al/Cu Al/Cu Al/Cu Al/Cu Bath
Metal Metal Metal Metal Metal Bath Stabilizing Sidewall Sidewall
Sidewall Sidewall Sidewall Stabilizing Agent Etch-Rate Etch-Rate
Etch-Rate Etch-Rate Etch-Rate Agent Added Solution at 25.degree. C.
at 30.degree. C. at 35.degree. C. at 40.degree. C. at 50.degree. C.
Solution Added (Wt. %) pH (.ANG./min.) (.ANG./min.) (.ANG./min.)
(.ANG./min.) (.ANG./min.) N1 5-Sulfo- 2.8 11.94 0* 5* 10* 35*
salicylic Acid K1 None 0 11.78 1 1 1 1 K2 Acetone 2.8 11.81 26
Oxime N4 Resorcinol 2.5 11.78 >34 (Al lines removed) N2
2-Hydroxy- 2.8 11.80 0 0 2 4 pyridine K41 2-Hydroxy- 5.0 11.90 0 0
1 3 9 pyridine N5 2-Hydroxy- 6.0 11.83 0 pyridine N3 4-Hydroxy- 2.7
11.80 0 0 2 4 pyridine *Etch-rate is based on a 10 minute treatment
since a 40 minute treatment completely removed the aluminum lines
from the wafer at higher temperatures.
TABLE 7b FE-SEM Cleaning Evaluation Results for Wafer #8 at
40.degree. C. Bath Amount of Al--Cu Amount of Amount of Stabilizing
Bath Stabilizing Metal Sidewall Wafer Sample Ash Residue Aluminum
Agent Agent Added pH at Etch-Rate at 40.degree. C. Process Time
Removed Metal Solution Added (Wt. %) 25.degree. C. (.ANG./min.)
(min.) (%) Etching K1 None 11.78 1 20 100 None N2 2-Hydroxy- 2.8
11.80 4 20 100 Slight pyridine N5 2-Hydroxy- 6.0 11.83 0 20 98 None
pyridine N5 2-Hydroxy- 6.0 11.83 0 40 100 None pyridine
Referring to Table 7a above, solution "N1" contains more TMAS and
glycerol than solutions K41 and N2-N5 shown above so as to help
compensate for the added aggressiveness towards aluminum metal
caused by the bath stabilizing agent 5-sulfosalicylic acid (due to
metal complexing) at 25.degree. C. However, the aluminum etch-rates
increase markedly at higher temperatures for solution "N1".
Solution "N4" utilizes the bath stabilizing agent resorcinol, which
is also known to be an effective metal complexing agent and also
imparts additional aggressiveness to the formulation towards
aluminum metal. While the addition of more TMAS would help to
reduce the aluminum etch-rate the "process time window" would be
reduced as shown below in Example 8. The addition of the bath
stabilizing agents 2-hydroxypyridine or 4-hydroxypyridine (supplied
by Aldrich) to the formulation is unique in that the aluminum
etch-rate appears to be reduced while stabilizing the solution to
prevent a change in pH during use. Therefore, the 2-hydroxypyridine
and 4-hydroxypyridine appear to be acting as aluminum corrosion
inhibitors in these formulations and can be seen as the
concentration is increased as shown in Table's 7a and 7b. If
necessary, the amount of glycerol may be decreased to raise the
aluminum metal etch-rate and enable residue removal in shorter
treatment times.
Example 8
Sections from wafer sample #8 were treated for various times in
each of four solutions, removed, rinsed with de-ionized water,
dried with pressurized nitrogen gas, Pd--Au coated and then
inspected in a Field Emission Scanning Electron Microscope
(FE-SEM). The FE-SEM inspection was used to determine the amount of
residue removal and aluminum metal sidewall etching that had
occurred during the treatments. All solutions outlined in the table
below were capable of cleaning wafer sample #8 in about 5 minutes
at room temperature. In cases where no treatment data was available
for a particular time, the aluminum metal sidewall etch rates
determined above in Table 7a were used to calculate the amount of
etching that would occur at that particular time. Based on this
calculation, a determination as to whether an acceptable amount of
etching would be expected was made and assigned for that particular
treatment time. The results are shown in Table 8a below.
TABLE 8a Process Time Window Comparison for Wafer #8 at 40.degree.
C. Solution Cleaning/Etching Performance by FE-SEM (Pass/Fail) N1
K41 N3 (2.8 wt. % (5.0 wt % (2.7 wt % Process K1 (No
5-Sulfosalicylic 2-Hydroxy- 4-Hydroxy- Time at Stabili- Acid
pyridine pyridine 40.degree. C. zer Stabilizer Stabilizer
Stabilizer (min.) Added) Added) Added) Added) 5 PASS PASS* PASS
PASS* 10 PASS FAIL (Clean, PASS PASS* but had Excessive Etching) 15
PASS* FAIL** PASS* PASS* 20 PASS* FAIL** PASS PASS* 25 PASS* FAIL**
PASS* PASS* 30 PASS* FAIL** PASS FAIL** 35 PASS* FAIL** FAIL**
FAIL** 40 PASS FAIL** FAIL (Clean, but FAIL (Clean, but had
Excessive had Excessive Etching) Etching) *Based on the aluminum
sidewall etch-rate known for this solution the sample would be
clean with an acceptable amount of aluminum sidewall etching.
**Based on the aluminum sidewall etch-rate known for this solution
the sample would be clean with an unacceptable amount of aluminum
sidewall etching.
TABLE 8b Process Temperature Window Comparison for Wafer #8a for 20
Minute Treatment Time Solution % Cleaning/Etching Performance by
FE-SEM N2 K41 N3 Process N1 (2.8 wt. % (5.0 wt. % (2.7 wt. % Temp.
Used (2.8 wt. % 2-Hydroxy- 2-Hydroxy- 4-Hydroxy- for 20 min. K1
5-Sulfosalicylic pyridine pyridine pyridine Treatment (No
Stabilizer Acid Stabilizer Stabilizer Stabilizer Stabilizer
(.degree. C.) Added) Added) Added) Added) Added) 25 100%/slight
90%/none 90%/none 85%/none 30 100%/slight 95%/none 99%/none
90%/none 35 99%/none 100%/none 98%/none 40 100%/none 100%/light*
100%/none 100%/none 100%/none *10 minute treatment.
Referring to Table 8a above, clearly there is an advantage in using
either 2-hydroxypyridine or 4-hydroxypyridine as a bath stabilizing
agent added to solutions similar to "K1" to maintain a large
cleaning process window. A large process time window is desirable
for flexibility in the manufacturing process. Referring to Table 8b
above, there is a clear advantage in adding the bath stabilizing
agent 2-hydroxypyridine or 4-hydroxypyridine in terms of the metal
corrosion that occurs during treatments at various process
temperatures.
Example 9
Wafer sample's #7 and #9 with 0.3-0.5 micron wide by 0.5 micron
deep holes (vias) through dielectric and titanium nitride layers
exposing aluminum-copper alloy metal at the base had been
previously processed as follows (a) metallization with
aluminum-copper followed by titanium nitride (b) coated with
silicon oxide dielectric using chemical vapor deposition (c)
lithographic patterning of vias using a photoresist material (d)
pattern transfer to the dielectric layer using a reactive ion
etching (e) oxygen plasma ashing to remove most of the residual
photoresist, but leaving mainly inorganic residues behind, were
used to evaluate the performance of the solutions. A sample from
wafer #7 and #9 was placed in solution's "L1" and "L2" at
45.degree. C. for 10 minutes, removed, rinsed with de-ionized water
and dried with pressurized nitrogen gas. After drying, the sample
was inspected on a Field Emission Scanning Electron Microscope
(FE-SEM) to determine the extent of cleaning and/or corrosion of
the metal features. The results are shown in Table 9.
TABLE 9 FE-SEM Cleaning Evaluation Results for Hydroxylamine-Based
Solutions Amount of Bath Bath Stabilizing Wafer Sample Amount of
Ash Amount of Stabilizing Agent Wafer Process Residue Aluminum
Agent Added Sample Conditions Removed Metal Solution Added (Wt. %)
Number (min./.degree. C.) (%) Etching L1 None 0 7 10/45 100 Slight
L2 2-Hydroxy- 5.0 7 10/45 100 Slight pyridine L1 None 0 9 10/45 100
Slight L2 2-Hydroxy- 5.0 9 10/45 100 Slight pyridine
Referring to Table 9 above, it is apparent that the addition of a
bath stabilizing agent to a aqueous, hydroxylamine-containing
solution has little effect on the cleaning performance of the
formulation, while significantly decreasing the pH change with time
that occurs with an aqueous, hydroxylamine-containing formulation
(see Table 5 above).
Example 10
Aqueous, stabilized solution "N6" was prepared with 1.5 weight
percent tetramethylammonium hydroxide (TMAH), 0.1 weight percent
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA), 0.06
weight percent of the non-ionic surfactant Surfynol-465 (a product
of Air Products and Chemicals, Inc.), 0.13 weight percent
(calculated as % SiO.sub.2) tetramethylammonium silicate (TMAS),
5.5 weight percent glycerol and 2.8 weight percent of the bath
stabilizing agent 2-hydroxypyridine (remainder of this solution
being made up with de-ionized water) and has a pH of about 11.85 at
25.0.degree. C.
Comparative uncovered 4 L baths with magnetic stirring at a rate of
150 rpm were set up in a chemical fume hood with an air-flow rate
of about 100 feet per minute (FPM) over the baths. The temperature
of the baths was maintained by use of programmable digital hot
plates with a bath temperature monitoring probe. The weight of the
solution added to the 4 L beaker is known and the total weight of
the solution, beaker and stir-bar is measured before and after
aging the baths at 40.degree. C. Samples were processed both before
and after the 24 hour aged bath is reconstituted with de-ionized
water to adjust for evaporative water loss. Sections of wafer
sample's #8 and #8a were placed in each 24 hour/40.degree. C. aged
4 L bath solution prior to stopping the aging test, removed, rinsed
with de-ionized water and dried with pressurized nitrogen gas.
Next, after 24.5 hours aging, the total weight of the solution,
beaker and stir-bar is taken and the total water loss calculated
for bath re-constitution. A sample of the 24.5 hour aged 4 L bath
solution is then taken and reconstituted with de-ionized water by
weight. Next, the solution is heated back up to 40.degree. C. with
stirring for processing for 20 minutes, removed, rinsed with
de-ionized water then dried with pressurized nitrogen gas. After
drying, the samples were inspected on a Field Emission Scanning
Electron Microscope (FE-SEM) to determine the extent of cleaning
and/or corrosion of the metal features. The bath aging results are
shown below in Table 10. Note: wafer sample #8a was prepared in the
same way as wafer sample #8 with the exception that changes were
made in the wafer etch/ash procedure that made the residues more
difficult to remove than wafer sample #8. A minimum cleaning
temperature of about 40.degree. C. was required by the aqueous
solutions shown in Table 10 for wafer sample #8a. A minimum
cleaning temperature of about 25.degree. C. was required for wafer
sample #8.
TABLE 10 4-Liter Uncovered Bath FE-SEM Cleaning Comparison of
Unstabilized to Stabilized Solutions Amount of Bath Wafer Residue
Residue pH Bath Stabilizing Sample Bath Removed? Removed?
(25.degree. C., Stabilizing Agent Wafer Process Aging (No DI
(Reconst. No DI Agent Added Sample Conditions Time Water with DI
water Solution Added (Wt. %) Number (min./.degree. C.) (Hours)
Added) Water) added) K1 None 0 8 10/40 0 YES 11.78 K1 None 0 8
10/40 20 NO NO 11.57 (90% clean) K1 None 0 8 10/40 24 NO 11.50
(11.47 with water added) K1 None 0 .sup. .sup. 8a 10/40 0 YES K1
None 0 .sup. .sup. 8a 10/40 <8 NO N6 2-Hydroxy- 2.8 .sup. .sup.
8a 20/40 0 YES 11.85 pyridine N6 2-Hydroxy- 2.8 .sup. .sup. 8a
20/40 24 NO YES* 11.82 pyridine (98% (11.81 clean) with water
added) K41 2-Hydroxy- 5.0 8 20/40 0 YES 11.90 pyridine K41
2-Hydroxy- 5.0 8 20/40 24 YES 11.89 pyridine K41 2-Hydroxy- 5.0
.sup. .sup. 8a 20/40 0 YES 11.90 pyridine K41 2-Hydroxy- 5.0 .sup.
.sup. 8a 20/40 24 YES YES* 11.89 pyridine (11.88 with water added)
K42 2-Hydroxy- 5.0 8 20/40 0 YES 11.89 (No pyridine metal chelating
agent added) K42 2-Hydroxy- 5.0 8 20/40 24 YES 11.87 (No pyridine
metal chelating agent added) K42 2-Hydroxy- 5.0 .sup. .sup. 8a
20/40 24 YES YES* 11.87 (No pyridine (11.87 metal with chelating
water agent added) added) *Solution bath aged 24.5 hours at
40.degree. C.
Referring to Table 10, the data shows the benefits of adding a bath
stabilizing agent to a solution to extend it's cleaning bath-life
to greater than 24 hours. The data also clearly indicates that the
efficiency in cleaning (without needing to reconstitute the bath
with de-ionized water after aging 24 hours) and pH control
increases with the concentration of the bath stabilizing agent.
Additionally, the data indicates that the addition of an optional
metal chelating agent is not necessary to effectively clean
residues from the wafer samples before or after bath aging.
Example 11
Aqueous, stabilized solution "O1" was prepared with 2.03 weight
percent tetramethylammonium hydroxide (TMAH), 1.56 weight percent
stable hydrogen peroxide and 0.14 weight percent (calculated as %
SiO.sub.2) tetramethylammonium silicate (TMAS) with the remainder
of this solution being made up with de-ionized water.
Aqueous, stabilized solution "O2" was prepared with 2.13 weight
percent tetramethylammonium hydroxide (TMAH), 1.55 weight percent
stable hydrogen peroxide, 0.11 weight percent
trans-(1,2-cyclohexylenedinitrilo)tetraacetic acid (CyDTA) and 0.14
weight percent (calculated as % SiO.sub.2) tetramethylammonium
silicate (TMAS) with the remainder of this solution being made up
with de-ionized water.
Aqueous, stabilized solution "O3" was prepared by combining with
2.02 weight percent tetramethylammonium hydroxide (TMAH), 0.12
weight percent diethylenetriaminepenta(methylenephosphonic acid)
(DETAP), 1.58 weight percent stable hydrogen peroxide and 0.14
weight percent (calculated as % SiO.sub.2) tetramethylammonium
silicate (TMAS) with the remainder of this solution being made up
with de-ionized water and has a pH of about 11.50 at 22.5.degree.
C.
A sample from wafer #7 was placed in each of solutions "O1"-"O3" at
22-35.degree. C. for 20 minutes, removed, rinsed with de-ionized
water and dried with pressurized nitrogen gas. After drying, the
sample was inspected on a Field Emission Scanning Electron
Microscope (FE-SEM) to determine the extent of cleaning and/or
corrosion of the metal features. A comparison of freshly-prepared
solutions to solutions aged at room temperature in sealed poly
bottles was done. The results are shown in Tables 11a and 11b.
TABLE 11a FE-SEM Cleaning Evaluation Results for Hydrogen
Peroxide-Based Solutions Solution Aged in a sealed Bottle for
Freshly Prepared Solution approx. 2 Months at Room Temp. Wafer
Amount Amount Metal Sample Unaged of Ash Amount of Aged of Ash
Amount of Chelating Wafer Process pH/ Residue Aluminum pH/ Residue
Aluminum Agent Sample Conditions % H.sub.2 O.sub.2 Removed Metal %
H.sub.2 O.sub.2 Removed Metal Solution Added Number (min./.degree.
C.) (22.5.degree. C.) (%) Etching (22.5.degree. C.) (%) Etching O1
None 7 20/22 11.5/1.5 99* None --/0.5** O2 CyDTA 7 20/35 11.6/1.5
100 None 11.7/1.4 100 Very Slight O3 DETAP 7 20/35 11.5/1.5 100
None 11.5/1.4 100 None *100% cleaning is expected for a 20
min./35.degree. C. treatment. **Aged 1 month at room temperature in
a sealed poly bottle.
TABLE 11b FE-SEM Cleaning Evaluation Results for Hydrogen
Peroxide-Based Solutions Wafer Solutions Aged for 13 Months Metal
Sample Amount of Chelating Wafer Process Aged pH/ Ash Residue
Amount of Agent Sample Conditions % H.sub.2 O.sub.2 Removed
Aluminum Solution Added Number (min./.degree. C.) (22.5.degree. C.)
(%) Metal Etching O3 DETAP 7 20/35 11.8/1.1 100 Light
Referring to Tables 11a and 11b above, it is apparent that the
addition of a chelating agent is optional for freshly-prepared
solutions. However, if the solutions are to be pre-mixed with
hydrogen peroxide added then the addition of CyDTA or a phosphonic
acid chelating agent has a significant influence on the solution's
stability as can be seen by the hydrogen peroxide concentration.
Since hydrogen peroxide is slightly acidic, the pH will increase
due to trace-metal catalyzed decomposition of the hydrogen
peroxide. Trace metals in hydrogen peroxide are known to increase
the rate of decomposition and the presence of a metal chelating
agent in the solution will drastically reduce the decomposition
rate. However, the chelating agent must also be resistant to
hydrogen peroxide decomposition. It is also apparent that DETAP is
more stable to hydrogen peroxide than CyDTA based on the relative
pH changes. While CyDTA increased in pH by 0.1 units in 2 months
the DETAP did not increase in pH over the same period. Even after
13 months the DETAP-based solution "O3" only increased in pH by 0.3
units.
Example 12
Each of the solutions "O1"-"O3" were aged for up to 13 months at
room temperature in a sealed poly bottle with a portion of each
solution taken periodically for a hydrogen peroxide assay. A
comparison of the amount of hydrogen peroxide remaining for the
three solutions over time are shown below in Table 12.
TABLE 12 Hydrogen Peroxide Decomposition With and Without Chelating
Agent Added Over Time Metal Chelating Wt. % Hydrogen Peroxide
Remaining After Aging at Room Temp.: Agent 0 1 2 3 5 6 13 Solution
Added Months Months Months Months Months Months Months O1 None 1.5
0.5 0.2 O2 CyDTA 1.5 1.4 1.2 0.3 O3 DETAP 1.5 1.4 1.3 1.2 1.1
Referring to Table 12, it is apparent that the addition of CyDTA
slows the decomposition rate of hydrogen peroxide over a period of
several months. It is also apparent that the phosphonic complexing
agent DETAP is superior to CyDTA over an extended period of time
(more than 1 year) at room temperature in terms of slowing the
hydrogen peroxide decomposition rate. While hydrogen peroxide does
act as a bath "stabilizing" agent, its own long-term stability in
the bottle to decomposition needs to be assured by the addition of
an oxidation-resistant metal chelating agent. Hydrogen peroxide
also acts as a "titanium residue removal enhancer", which depends
on a critical concentration in order for effective cleaning to
occur. If the hydrogen peroxide decomposes below this critical
concentration then two things will occur: (1) excessive corrosion
of the aluminum metal will occur due to an increase in the pH of
the solution (hydrogen peroxide is slightly acidic) and (2) the
titanium-containing residues such as those found in wafer sample #7
will not be cleaned.
Example 13
Copper corrosion inhibitors were tested in aqueous, stabilized
solution "A1" by adding 0.1 weight percent of the inhibitor for
each test. Copper metal foil was cut into coupons with the coupon
dimensions kept constant. The coupons were pre-cleaned to remove
the surface oxide using hydrochloric acid followed by a de-ionized
water rinse and dry. These copper foil coupons were then
pre-weighed on an analytical balance. The capped bottles of test
solutions were pre-heated at 65.degree. C. for one-hour prior to
adding the coupons. The heated solutions were removed from the oven
and the coupons were then immediately added to the bottles
containing the test solutions, re-capped and then placed back into
the oven. After 24 hours in the oven, the coupons were removed,
rinsed with de-ionized water and dried. The copper coupons were
then weighed on an analytical balance and the resulting copper
metal etch-rates calculated. The results are shown below in Table
13.
TABLE 13 Copper Metal Corrosion Rate Comparison for Solution "A1"
with Copper Corrosion Inhibitors Added Copper Metal Etch-Rate
Inhibitor Added (Angstroms/hour) None 200 Benzotriazole 140
5-Methylbenzotriazole 30 Benzotriazole-5-carboxylic 170 acid
5-Chlorobenzotriazole 40 5-Nitrobenzotriazole 80
Referring to Table 13, it is apparent that the addition of a copper
corrosion inhibitor decreases the solution etch-rate on copper
metal for a stabilized aqueous solution. This would minimize any
unwanted copper etching that would occur for a solution of this
type while still allowing the removal of copper-containing etch
residues.
The invention has been described and illustrated with various
illustrative embodiments thereof. It will be appreciated that these
embodiments are not limiting and that various modifications and
changes may be made without departing from the spirit and scope of
the invention.
* * * * *